Eh i've done it plenty of times while playing and honestly the main reason tends to be for me anyways that I expect the jungler to get there sooner than they actually can/ did espcially when they play more mobile champs.
Another reason being is I expect them to come from one way then they walk all the way around like you said (nothing wrong with walking all the way around like that but if you are on your way and i see you nearby I might think you are coming as fast as possible espcially if they are at our tower not walk around to get behind them)
And maybe ping it later? If they always go in well before then ping it like 5 seconds before you'd arrive that way they can't start it way before you get there and if they do start the fight you are at least in range to clean up assuming they aren't completing useless. Not really sure when you start pinging though but I mean if you ping it while you are in the tribush/ walking out of it then i don't see really see how they would end up starting it way before you get there.
Doesn't happen often at all that I've done that but over years of playing I've definitely did it more times than I'd like to admit and I'm sure I'll end up doing it again eventually.
I also don't see twitch jungle alot so maybe they don't either and thats part of the issue? I used to main Shaco and lots of times my team would start going in before I got there so the enemy walks away making the gank harder or getting so far away I can't even get ontop of them. Whereas if they waited for me to simply be near them invisible then go in it'd be too late for the enemy. Team mates literally announce "hey we are ganking you" when they suddenly play differently/ more aggressive they don't even let you actually get there first.