When I was a kid too I had a lot of the testors stuff as well, paint, glue, drop cloth, the works.
Now I use stuff from all over the place, Testors, Micro-Mark, Squadron, Tamiya, the hardware store, etc.
With me it has to do with personal preference, availability, and/or cost.
For an example I'll show you a little of what my breakdown is:
Paint: Testors Model Master with a few Humbrol and Tamiya paints
Thinner: Lacquer and Low Odor thinner available at the hardware store.
Glue: Zap brand CA, Tamiya and Micro-Mark brand liquid cement, Testors and G-S Supplies for clear parts.
Squadron Brand putty (I mostly use CA for filling though)
Tools: Some are hand me downs, others I bought or got as gifts.
Airbrushes: 1 Aztek and 2 Badger
There's more but you get the idea. The tools and even some of the paint took 15+ years to acquire.