It doesn't, I can't wire an amp head into it therefore it isn't a cab.
I use a backline anyway but almost always with a di to the foh,the point was I'd only ever do a gig with that band knowing what I needed before hand, if in the future I have iem or just use a wedge it will be me taking it and setting it up, if it was a bigger gig I'd be hiring in a bigger PA that would be spec'd to suit likewise.
If you are in a band where you don't know what will be there like your typical 4 bands on the bill job or a charity all dayer then a cab is required imo even if it's a 300 watt 2x10 combo.