They make it that annoying so you'll pay for a premium account that removes all the annoying crap (and improves speed, removes download caps).
And anyway, they provide a valuable service: illegal file sharing using only Google and HTTP. I've long since abandoned networks like gnutella, edonkey, bittorrent, etc in favor of a good blog search engine and file-downloading sites. Similarly there's hundreds of streaming video sites to watch TV series on without the need to download. I can ignore an ad here or there for the convenience of pirating media from any web browser in the world.
Bandwidth costs money. Hosting costs money. They can't just let hundreds of thousands of people download gigabytes at a time at >5Mbps for free. Peer to peer networks don't have huge resource drains on anything but the bandwidth of ISPs.
And anyway, they provide a valuable service: illegal file sharing using only Google and HTTP. I've long since abandoned networks like gnutella, edonkey, bittorrent, etc in favor of a good blog search engine and file-downloading sites. Similarly there's hundreds of streaming video sites to watch TV series on without the need to download. I can ignore an ad here or there for the convenience of pirating media from any web browser in the world.