Some guitarists like to use old tube amps because they can be repaired, maintained, and modified much more easily than their modern counterparts. Old tube amps tend to have point to point wiring, which is much easier to fiddle with than reflow soldered PCBs.

Electric guitarists are often poor, clever, and self reliant. They can regularly find themselves out in the boonies with nothing but duct tape and baling twine to hold their rig together. Choosing a more robustly built older amp is not an irrational choice for such a person.