And this website is a lot more approachable than Smogon, at least in my opinion. And the people using this site are of this community, and it's wrong to say that just because someone else is doing something, you should give up (even if they're more successful). That's just inviting monopolies on subjects. But as others were quick to point out, your logic would suggest obliterating other sections of the site.
And PokemonDB has certain strengths over other sites with Pokemon data.
The overall data on this site might not be as extensive or in-depth as Bulbapedia, but Bulbapedia is a very slow site these days. It sometimes takes several minutes just to navigate to a page. Compare to this website, which runs silky smooth even on a Nintendo 3DS web browser.
I would personally feel more comfortable getting a rating from someone on this site, as I know this site well, rather than make an account on Smogon and ask.
That's just my personal mindset, obviously plenty of people don't care about that.
Plus, Smogon has a 13+ age rule. Even if you lie about your age or don't mention it, it's technically less inviting.
I think the RMT has a lot of room to grow but it still serves a function and removing it would be a shame. Much better to evolve and improve it. I mean, it's not harming anything by existing. If you prefer Smogon you can just use Smogon.