When bitcoin adoption grow, altcoins potential adoption grows as well. As bitcoin is more tested and developed altcoins also get benefited by that.
Market usually don't care about technology or the base. Besides, cryptocurrency which isn't forked from Bitcoin or Bitcoin Core source code usually have some major difference on technology.
I agree, regulation for altcoin usually follow bitcoin regulation, unless there's explicit regulation for altcoin such as restriction for privacy-focused altcoin such as Monero.