Doctor Who (2005) isn't called a reboot. It is called a continuation of the old series. This was made possible by that regeneration ju-ju and stuff.
On the other hand, Star Trek 2009 reincarnation is often called a reboot. Nobody dared call it continuation. I don't think I need to do citation because it's common.
Now, if we actually go into the details:
The new universe contains two Spock. One is from the original timeline. The Spock Prime even gives data from the original timeline like trans-warp equation, Khan etc.
We see other past data from before the timeline diverged. For example, Scott told that he transwarped Admiral Archer's dog. "Archer's dog" existed in Star Trek: Enterprise TV series.
So, why didn't the legacy survive in-universe? Why isn't it considered a continuation of the old Star Trek TV shows and movies?
Or, is the reboot word used by mistaken fans and media only?
After the release of Star Trek: Beyond (2016), this is no longer a confusion as the movie showed a photo from original timeline.