The hostel bar
Almost every hostel has some kind of entertainment. Whether it is in the same building, or a nearby bar that get populated with backpackers overnight. If you have just arrived this can be a nuisance with the onset of jet lag.
Certainly with the larger hostels I have been to, when arriving by night you might here the unmistakable sound of PDP Drums. The odd hostel bar does have live music but often its usually a resident DJ.
You could just go into town and see the locals, which is always welcome when you have been staying in a hostel for a prolonged period of time. Certainly this would be the case if you have taken a job in the area to save for further travels.
But if you have just arrived then this is an ideal opportunity to network with other travelers. Quite often as a newcomer you'll probably be invited out by dorm mates. Maybe even find a travel buddy to go exploring with.
Its far more than cheap drinks at the bar. Although hostel bars are not for everyone, and some hotel bars are probably dives that are best avoided. Of course there are those drink promotions you get when you check in.
The important thing to remember is not to waste your travel funds, and yes I have seen people squander their budget on alcohol which really isn't why you jetted half way around the world.