In case you are interested, SimGuruGrant talked a bit more about the reasons for their decision on twitter.
He said it was not to avoid lag in the game that they didn't include snow depth.
https://twitter.com/SimGuruGrant/status/1001877966874263552
He also said the decision was taken because of the characteristics of the engine used in Sims 4, and not because of a problem in the way worlds were built.
https://twitter.com/SimGuruGrant/status/1001877150843064320
https://twitter.com/SimGuruGrant/status/1001878994181021696
I really hope some of the new aspects of seasons brought by the characteristics of this engine will make up for the absence of real snow.