Well, there are a lot of factors at work here.

While wallets and keys ARE tricky for the average person to understand, the stigma of crypto=scam is still prevalent. Whether it's the fact that some of the loudest voices on nostr are vocally pro-bitcoin, the fact nostr integrates bitcoin by default, the constant shitcoin spam, or the mere mention of cryptography in general if the average end-user sees any of this they nope the fuck out. I do understand that a lot of that can be solved with a larger user base diversifying the type of topics being talked about, but the problem is getting enough growth and more importantly, retention to have that.

Bluesky sets out to have one role, to be a Twitter alternative. Nostr, on the other hand, is trying to be a Twitter alternative, a Reddit alternative, a Spotify alternative, a Craig's List alternative, a Twitch alternative, etc. Nostr is predominantly advertised to others as a Twitter alternative. Still, when people join and stick around long enough to see other apps, they MAY end up being confused as to what nostr actually is.

Another thing Bluesky has going for it right now is the fact that there's a single gateway into the ecosystem. While it's not necessarily a good thing in the long run, for now, it's good because it reduces the confusion of new users as to where to actually go. It also helps set a base list of features that other clients should implement. Nostr, on the other hand, has many different clients with many different feature sets. While this is ultimately a good thing, you start to run into the problem of keys becoming less and less portable because clients are introducing more and more features that other clients aren't implementing, thus potentially breaking clients. Focusing on a smaller number of clients will really help with that.