1. lack of support from payment processors to go out and do sales pitches to businesses:-
 i have personally told bips, bitpay and coinbase of 5 merchants that wanted more info. and as of yet (upto 1 year in one case) the merchants have not had a single response from the gateways

2. software is still in beta phase and not ready for average joe (7billion population) daily spenders:-
a truly trusted service that actually adheres to consumer protection guidelines (liability insurance to protect customers holdings) to then be used as a offchain service for pre-confirmed funds, making it an instant use wallet to send funds as small as 1sat to merchants.

3. hardware/cold wallets are still in beta. yes trezor(hardware) and HD-01(coldstore) are still not 100% secure or easy to use for long term large storage.

4. bitcoin protocol is not ready to handle heavy volume, it is also not adhering to consumer requirements, but it is more twisted in favour to miners greed.
lets see 'death and taxes' appear with rebuttals to defend the miners honour, like always

in short, we are still in the innovator/early adoption stage.. we have a long way to go yet before being in the mass adoption: public stage