This is nothing to do with libraries being good or bad value though.

Libraries are not advertising funded because advertisers are not very interested.

If advertisers were interested then these libraries would likely be just as infested with adverts as the internet.

If we tried to fund the internet in the same way as libraries advertisers would still be strongly incentivised to show adverts and would still work hard to find ways to do so. So it's not clear the situation would change much if there was government funding for content creators.