No martial art is that useful IRL. Might as well do one you enjoy.
I'm do Muay Thai right now, it's actually pretty useful....trust me 
Just wanted some grappling stuff to go with it.
Until some cvnt pulls a knife on you, lol. You'll deal more damage to somebody you're trying to get the fark away from than somebody who wants to keep you in one spot to 'fight' you will deal to you, anyway; no such thing as a spar if somebody wants to gut you.
It'd be useful if they're much stronger than you and you needed an edge in a fight, but that would generally require you staying to fight them. If they want to kick your arse, you have no reason to stay and you lose the advantage by doing so. If you want to kick their arse, they have no reason to stay, so they have the advantage.
If you legitimately want to hurt somebody, you either have to take them out straight away or make sure they can't turn the tables with weapons (either ones they already have on them or makeshift ones) or by calling in friends. Going in for a grapple or something is insanely risky when they could reach behind their back and prison yard rush you before you even realise what's going on, leaving you on the ground trying to hold your guts in.