Every single file sharing client other than bittorrent had search. BitTorrent easily beat them all. You can argue if you want that this is a pure coincidence, but it's not going to be very convincing.
Why do you think decentralized technologies still help people pirate software to this day while centralized services eventually gets shut down? The amount of trackers that has disappeared over the years is huge, and some of them quite sad as well. What.CD would be a famous example where we basically had a enormous backup of long lost music in the world. What.CD disappeared when French authorities managed to figure out where the servers were and got permission to raid them.
Same thing happened with TPB a couple of times, but amazingly it's still standing. We can only hope it remains so, but in the future we might not be as lucky. Not to say that plenty countries block access to TPB via having the ISPs block DNS/IP to known addresses.
All of these things wouldn't have been a problem if the search index was also decentralized.
You had a gigantic list of servers and didn't have to care if law enforcement managed to ban a few dozen? You could also search for anything shared by your peers. Major downside was that it wasn't curated and files tended to be shared under a dozen different names, so just because you think you were downloading Debian.iso didn't mean that it wasn't xXx_AnalCompilation5_xXx.avi, you had to check which name was the most frequent to be sure.
