I have a feeling this has a lot to do with the pets! I mean let's face it, all pets we have are pretty small, dogs, cats... If they were to run into deep snow, they would need to design and program a lot of snow effects, such as tunnels of snow, because of the dogs rushing through it etc. I am sure part of this decision had to do with something like this. If they say it does not look that good, I wonder why they did not decide to show us pictures of HOW it actually would have looked like and then let the people decide... That would have been a great movement from the producers and designers. But no rather than showing us what we could have expected with deep snow, they just decide without the people's view on things.
It's not a deal breaker for me either, but it's quite sad that an old game such as Sims 3 had deep snow, but Sims 4 can't do it? Maybe they miscalculated the abilities of the new engine and truly did not think it through that at some point seasons would be implemented again.