Shitcoin wallets often aren't trusworthy or secure. Someone was just recently posting about how they lost bitcoin making a transaction with cake wallet.
No matter how easy a wallet claims to make the swap there is still an opportunity cost to holding monero instead of bitcoin. The exchange value floats & monero does not hold value the way bitcoin does.
If there is a large bitcoin only ecosystem, & there is a shitcoin friendly ecosystem, but the common denominator is that everyone accepts bitcoin, then Bitcoin's network effect ultimately drowns out everything else.
Current darknet markets are a deadend. The next iteration will be on networks that are more user friendly & more robust than tor, & some layer on bitcoin (probably ecash that swaps to lightning) will likely be the currency of choice. All of the serious p2p projects I know of are being built by bitcoiners.