I’ve never completely understood this, but I think the answer would probably be “no,” although I’m not sure. Usually when I leave the house I turn off wifi and just use mobile data (this is a habit from my pre-VPN days), although I guess I should probably just keep it on since using strange Wi-Fi with a VPN is ok (unless someone at Starbucks is using the evil twin router trick . . . ?). I was generally under the impression that mobile data is harder to interfere with than Wi-Fi, but I could well be wrong and my notions out of date. So, if need be, please set me straight. 🙂
I would stronly recommend that you set your wifi to only join trusted networks. That way you can also just leave the wifi on and not have it connect to every random network it encounters.
I would still recommend turning wifi off when leaving home for privacy reasons (which can easily be automated). The process to identify if a network is trusted or not requires a handshake. So leaving wifi on makes you trackable by the wifi network operators and the apps on your phone with access to your wifi, wether you connect a network or not.