Regular shoes? If he goes to public places like parks or a beach he really needs to have shoes and socks on to protect his health.
Many times people find razor blades that were used for cutting drugs, syringes, broken glass, and more in the sand of playgrounds. They also find mold, decomposed insects and animals, and fungus in playgrounds that have other types of surface.
Public play areas are not healthy for kids. I always clean their hands and faces before we get in the vehicle. They are covered with nasty stuff.
So if you're going somewhere you need the kids to wear sturdy shoes and socks will keep them from sweating in them and making them stink.