Is it really needed if the user only installs from play store and not from any dodgy sites?
You don't necessarily need one, but if you use banking apps, they may suggest you install one. Be strict on how you use the Google Play Store, don't install any app, check it's reputation and reviews, do background research if required.
Always keep apps updated and latest Android version, if and when available.
I personally prefer security apps that
only scan the app upon install / update. That's why I have previously used Bitdefender Free and now Zemana Mobile Security. In my opinion, Web Filters, Privacy Scanners and other features are junk. If you use Chrome for Android, you have some security and privacy choices.