Unless you are someone buying Transformers with the hopes of making a profit later down the line, reissues are great. If there were no re-issues the toy would likely be worth more but... we're talking mass produced toys sold on a global market by a giant of a toy company. They look at the market and decide what's most desired and capable of rendering a profit. I'd imagine they're, generally, not all that interested in making very defined, strict collectables.
Some vintage toys only bring wads of cash because, well, they're toys - they were beaten, battered, destroyed and thrown out. So, over time and production cancelations, their numbers went down. Nostalgia plays it's own hand too.