Not really. Think about the history of Glastonbury. It was about a hippy thing. Bullshit, of course, but a lot of bands associated with that, especially after the world moved on, tried to pretend they weren't about mainstream.
e.g Bands like Pink Floyd and Zepp didn't release singles (or at least not many) and when they did they generally didn't perform very well.
The idea is about being huge, selling lots of albums and tickets without actually being popular. It sounds like a paradox perhaps.
Now, of course, Glastonbury has never really been about that hippy ideal. In the same way that most rock bands have always been about making their entourage incredibly rich, to do that they have to sell an image. And that image is the idea it's "all about the music" and sometimes about some kind of faux highbrow thing to their music - hence the "concept album". It's all just a bullshit line to sell records to people who want to kid themselves that, somehow, Pink Floyd weren't like Take That or Westlife.
In the UK if you went to a wedding and they had a disco and you asked them to play some heavy rock, they'd play Status quo or maybe, if you were absolutely lucky, Since you've been gone by rainbow - that was about the limit of getting rock or heavy rock played anywhere where "ordinary people" were gathered.
Instead, you were supposed to shuffle off to your own pub or disco, dedicated to that genre of music. Never the twain shall meet.
Similarly lots of other genres existed with their own culture : skinheads, punk, goths - it's all about being partisan. Not about liking music, it's about getting young people's aspirations. The way they dress, the people they mix with, the records they buy - all associated with a subset of bands that play the same type of music - and shunning the rest.
Now, perhaps some rock bands stepped a foot into the mainstream more so than heavy rock did - but then often they would be looked down upon for that (e.g Nickleback effect) U2? No credibility at all. Coldplay? C'mon.
The point is, to have longevity - a long career where you are seen to have credibility - to be a band that's revered. To be selling records 10, 20, or 30 years after you were formed and long after one or more band members are dead, then being mainstream or popular is perhaps the worst thing that can happen. And I know it sounds paradoxical but there's a huge difference between the kind of popularity that a band like AC/DC, Led Zepp, Pink Floyd, Cream, The rolling stones, Jimmy Hendrix et al have enjoyed and that gained by, relatively speaking short-lived pop acts like the Spice Girls and so on.
I think in the USA it's less of a thing than here though. Perhaps I'm wrong. e.g back in 1984 they didn't seem to baulk at the idea of having Led Zepp play at Live aid, for example. Whereas the UK had Queen (who were largely a pop act by this stage - albeit they stole the show somewhat with their back catalogue) and Status quo (who, as I said, were the faux "heavy rock" act whose songs were rolled out so that your drunk aunts and uncles can pretend to headbang and play air guitar)
These days, of course, music isn't really mainstream at all. It doesn't make the money it once did, and since the artists can only really make money playing live they don't really want to be seen on TV playing their concerts (because they are afraid of people not turning up) Of course they have to try and balance that against getting some kind of publicity (and it's true to say that much of Glastonbury is televised, they tend to be showing subsets of the performances)