Most people were newbies in early 2010. When people join the forum today, it is often after doing a decent amount of reading and/or research about bitcoin. In 2010, there wasn't much reading to do about bitcoin outside of the forum.

It is interesting to see satoshi responding to new users with questions about bitcoin.

If satoshi were to come back to the forum and provide proof he is satoshi, anytime he would post, he would likely get dozens (if not more) replies, and people would be PM'ing him left and right, to the extent that it would be impossible for him to communicate with anyone.