The lack of rules for different types of wilderness in recent editions is sort of shocking to me, it seems like an obvious part of world-building. How do you NOT have rules for traveling and moving on ice, sand, snow, and through bogs? How do you NOT have classes and feats for adapting to extreme environments?
Well, there are little bits of such things here and there.
But the bottom line is this: they don't exist because most of the customer base just aren't all that interested. Handling snow and ice is a fairly niche topic, and handling
movement on snow and ice is a niche within that niche (and doing the same for sand, or bogs, or whatever is a
different, albeit closely-related, niche). They just don't justify putting in a lot of work.
And you can add to that the criticisms that WotC themselves make
of their own environment rules in the "Rules Compendium" - when they
do provide the rules they are often over-complex, not a lot of fun,
and very seldom see actual use at the table.
So we're talking about a topic that's already of limited interest, and one where even people who are interested don't use the rules that are provided. It's not a huge surprise they've started to de-emphasise such things!
(For what it's worth, I actively dislike the "Rules Compendium" precisely because of those sidebar criticisms - to a large extent they read as the designers actively rubbishing* the prior art in 3.5e in advance of their work on 4e. But part of the reason I dislike them is that while I like 3.5e a great deal, I have to admit there is significant truth in those criticisms - the environment rules in "Sandstorm", in particular, are far too complex.)
(Oh, and also for what it's worth, 4e generally took a better approach to this: environment rules actually
were defined, but they tended to appear where they were needed. That is, if an encounter featured icy and snow, then the relevant rules would appear in that encounter description. That was one of the very few benefits of the unlamented Delve Format for adventures. It also meant that two encounters in icy areas could actually use
different rules for ice if it was appropriate to do so, which is actually a
good thing - not all ice is created equal!)
* I'll freely admit that my impression of that book may well be unfair. But that was indeed my impression.