Which is precisely what my post was saying was an issue with existing policy. I find it a little odd that you'd respond to point out the norm, to a post complaining about the norm, and expect the norm to be in and of itself a justification.
Work created an additional cost via required travel. It isn't at all similar to your "clothing for meetings" example because you'd need those without the travel component. When travel itself creates additional costs: those costs should be compensated.
Maybe the norm is wrong and a company should cover those things. (And the kennel seems to be more directly connected to travel than my other examples.) But it's not really surprising that most don't.
I did work for a company once that had an "offshore inconvenience allowance" fr when we were on rigs and shipyards. It was mostly in the vein of living conditions aren't great and you're working long hours, so here's some extra money. So that's one relatively fair comp mechanism you can use. But mostly it's just baked into people's normal comp plans.
Because it's not the sort of expense that companies normally cover. Especially people who travel a lot have all sorts of second and third-order expenses resulting from the fact that they're away from home, may have to dress up for client meetings, etc. that are rarely covered by expense policies. They're also working extra hours when they travel. As partial compensation, many are also expensing fancier meals than they'd have at home--and are presumably being paid a competitive salary that reflects a fair bit of business travel.
Whether all this is "fair" is at least somewhat a value judgement but has been the approximate norm since I first traveled for work a very long time ago.