It's all a push in 2 directions: lead free and surface mount. Problem is, pretty hard to get big watts cheap in surface mount. I have had about 30 parts need re-sourcing in the last year. SOme are easy, same part, slight number change, other big-time PITA.
I have a few PCB's that we do some surface mount on, but it is small power, and low volume.
Just for laughs, I tried a re-do with surface mount FET's and stayed at 30% power to allow free-air cooling -- trippled the FET count, and it was over 5 times the PCB area.
Right now I can do two TO220 parts in nearly the same space of a DPAK surface mount, and get way more power out of the to220.
It's not just the distributers though, the plants are producing way less through-hole also.
Pick a non-stock part at the distributer level and then go upstream to the maker.... likely no stock there either.