“I can tell you why I have a gate. It’s not to keep out someone that REALLY wants to get in (as I can hop over in about 5 seconds if needed). It’s to keep randoms from coming up and knocking on my door.
I work from home a lot and hate when I get a knock on the door during the day (or at night when I’m spending time with my wife) only to go to the door and find some pandhandler ‘fundraising’ for a trip or other nonsense.
And while I don’t subscribe to the fact they’re a big problem, I have heard warnings that people come by, knock on the door for a ‘legit’ reason, and if no one answers they target the property to break in. A gate will keep most of these fishing expeditions out.
So a gate isn’t going to keep someone out that’s committed themselves to getting in, but it’ll be a deterrent to the passers by that want to bother you.
Other reasons? I park my car inside the gated area (yet still outside) so I add some security there. I have furniture on my patio that is much more secure due to the gate. I have a daughter that’ll soon play outside and I like the idea of her not being able to run out to the street. If I had a dog I could let them run around without bothering anyone walking by or running into the street.