The first thing that has to be addressed is that there are some bands which start out playing meaningful lyrics from their very first single. Because it would be incredibly hard to call someone whose never been anything but mainstream as selling out to the mainstream, we will ignore this group for now.
The truth of the matter is that bands cannot make the same songs over and over again. Why would people continuously spend money on buying new audio CDs and going to concerts if all they were going to hear is the same old thing? That may work for diehard fans, but not the casual ones who pack most of the stadiums and concerts. Bands have to change and adjust, like everyone else in life do, to keep their career promising in the future.
It also doesn’t make sense when people accuse bands of selling out after they sign with big record companies and play on MTV. The truth is that every band is made to make the big bucks and to be famous. By refusing to go mainstream it would be hard for any band to do this.
That being said, making more sensitive and serious lyrics shouldn’t go hand in hand with selling out. While blink-182 may have been happy all the time and felt good enough to not have to write anything but naked humor early, it is likely they witnessed more and more bad events occurring around them as they grew into their later ages. It is hard to keep all your emotions bottled up when you want to express feelings, so it is not a big deal that the band wanted to use harder events in their lyrics. I don’t think that makes them sellouts, even though they are much more of a mainstream band than they used to be.
In the end, blink-182 broke apart and no longer play together anymore. Many fans still existed for the band and they are still looking for a reunion. While this may or may not ever happen, one thing is for sure. The blink-182 who used to have nothing to do but run naked down a street while passing hot girls is probably gone forever. But their lyrics will be something that will touch us all forever.