'Need'? Not at all... but they exist, and I've been switching the thermostat from heat to cool and back often enough that it's gotten annoying. Especially so right after getting home from work when there's that contrast from a relatively cold AC'd car to a relatively cooked house; but my body temp is still on the chilly side so it feels comfortable long enough for me to plop my ass down and relax on the couch... only for that contrast to wear off over the next few minutes and I start getting uncomfortably hot and sweaty. So I turn the AC on, then tomorrow it randomly drops 20 degrees outside, and now I live in a refrigerator.
I just want to set it and forget it.
Ordered one of the Honeywell's. We'll see how it goes.