Ending most battles standing in every damaging surface and cloud known to science ain't fun. Makes things a hassle. It also does not fit in d&d.
There are already many 5e spells that have sustained aoe-effects, be it for CC or damage. We don't need another layer of effects on top of that.
I'm at a point where I try to avoid creating new surfaces as much as possible, because I hate how inconvenient they make looting and exploration of the area.
