Most merchants are not interested because of the perception that Bitcoin is a fringe currency and in many places because of the risk of debanking and general FUD around Bitcoin, plus the fact that so few people want to use Bitcoin so the potential for sales using Bitcoin is tiny. Merchants simply do not have sufficient incentive to accept Bitcoin. If a merchant asks his accountant 'whats involved with accepting Bitcoin' most accountants will advise its not worth the trouble of setting up the required systems. I believe it is a combination of FUD/misinformation and deliberate obstruction by banks and governments. Also 70% of humanity live under autocracies and few if any of those autocracies allow Bitcoin MoE. Of the 30% of humanity who live under so called liberal democracies the subtle but effective obstruction via tax obligations/implications prevents any real MoE use. Bankers and governments do not want Bitcoin challenging their fiat MoE hegemony and they have succeeded in obstructing it. So few Bitcoiners are even prepared to admit this problem that it seems unlikely to ever be addressed, let alone solved.