Given the actual correlations attacks governments have done on Tor traffic, I don't think more traffic moves the needle in any appreciable way. Ultimately the Tor architecture is very vulnerable to timing and correlation attacks (never use something like IRC over Tor), and the kinds of changes that would be needed to mitigate those would probably slow it down past the point of usability.

One could argue, given the limited bandwidth of the Tor network, that by using it when you don't need it, you make the experience for those that do need it worse (looking at you everyone who tries to torrent over tor).