If you don't get your vehicles wheels and axles aligned then if your wheels and axles are out of alignment then your tires will start to wear out unevenly.
You tires will start cupping and getting out of round and eventually the tire could blow out overtime.
If you put new tires on your vehicle be sure to get an alignment performed especially if your vehicles tires you replaced were wearing out unevenly.
Some tire shops will do an alignment included in the tire changing and some will do it with a discount if you buy the tires from the shop doing the alignment so check with the tire shop about an alignment.