This is a reflection of an age old problem, only substantially mitigated from the 1990s onwards. It is also an interesting element in terms of 'keeping going' over the course a long campaign. Without wishing to be in anyway condescending, the sheer relentlessness of 'campaigning' is not well understood by those who have not gone through it. In the infantry in particular, the state of the men's feet is a matter of critical importance. If you can't march, you can't fight, and if you can't fight you're in the way and just a hungry mouth to feed.
The wearing of gaiters is designed not to deflect problems with boot leather, but rather with human flesh....in the form of the old 'plates of meat'. The idea is to stop the lower trouser leg becoming drenched in damp long grass or similar foliage. Once the trousers are soaked, it is only a matter of half an hour before the moisture creeps down to the socks. (Of course heavy rain creates the same effect). When socks remain constantly wet, problems with the feet begin. It starts as unpleasant, (albeit you soon get used to it as a status quo), but over time moves beyond an irritation to become the cause of sore feet, wrinkling and blisters. After that comes the rotten flesh condition which has become known as 'trench foot'; a crippling ailment which renders a soldier ineffective. It might take some weeks to arrive at this, but campaigning typically goes on for months and even years at a time. In genuinely awful conditions, it can come on in a matter of days. So the first object of a gaiter is to shroud the trouser leg. The presence of a gaiter at least slows, but will not prevent, the gradual creep of moisture down the trouser leg - if you're really lucky the sun will come out after rain and dry the trousers before too much nuisance effect occurs down inside the boot (ie wet socks).
The second purpose of a gaiter is to make the effective top of a boot much higher and thus prevent the boot being flooded even in the shallowest puddle of water. Before 'Goretex socks', (actually over-socks as it were), and then, a few years later, goretex boots, came on the scene in the 1990s, the 'good infantry soldier' kept his boots layered with boot black in order to retain whatever limited 'waterproof' qualities they might possess (which in my youth was virtually none - if anything our boots of the 1980s were less waterproof than those of the late-Victorian soldier and the two World War generations). The single most important item of clothing in the good soldier's kit was his second pair of socks, which he would try to keep dry at all costs. The metaphorical 'good soldier', (only a proportion of the body of the kirk, the size of which proportion rather depends on the quality of the leadership cadre of officers and NCOs - the key difference between a good regiment and a shabby one), would, on reaching a bivouac, take off his damp socks and replace them overnight with his dry pair. This will give his feet some respite. His wet pair of socks he will lay out to dry - ideally on a sunny rock while it is still daylight: in a hot climate they'll be dry in half an hour. If it isn't hot, or daylight, or he is in some difficult environment, (such as the dense forest conditions of the Victorian era Gold Coast), he might have the opportunity to dry them near his camp fire (if he's allowed one - which will depend on tactical factors). If all else fails, he might well end up wedging his damp socks into his arm pits or his crotch for the night, (yes I know...yuk!...tell me about it!). He should then, before moving off for the next day's march, replace his best socks with his still probably slightly damp pair. It is only by devoting this level of sustained care and attention to his personal well-being that he can keep himself fit for duty, in field conditions, for months on end. It is the good soldiers who succeed in this object. It is a fact of life, in the great conundrum that is soldiering, that good soldiers will also be to the forefront of the 'charge', whether that charge, depending somewhat on era, be a metaphorical or a literal one. Thus the good soldiers may well be will be amongst the first to be 'attrited', (awful made-up word, but it conveys the relentlessness of campaigning well), over the course of a long spell of field service. I have observed that it is possible in military history to trace the gradual decline of a unit's professionalism/performance, it's courage even, as the good soldiers (and the leadership cadre of officers and NCOs) fall away from the Colours as casualties of disease or battle. So the fewer good blokes you lose, from any cause, the better. Thus seemingly inconsequential matters - decent boots, socks, gaiters etc - assume much greater importance than might at first seem apparent.
Most of the other soldiering of the Victorian era was done in hot dry climates, rendering gaiters less relevant. Gold Coast soldiering took place in a dank forest environment - a 'jungle' in all but name - where the maintenance of the feet becomes a doubly difficult proposition of course.
P.S. Knee-length puttees (not 'invented' in 1873-4), achieve the same effect as gaiters - which is another explanation of the apparent absence of long gaiters elsewhere.
Dr Mike Snook MBE psc