First thing, bitcoin is not only digital currency, it is 'digital crypto currency'. There is this difference. When we say online transaction what is that isn't it a digital money. Earlier plastic money (credit card) was there. It is still being used. Now mobile paying technologies are there. So people are using digital payment systems. With complete digital where there is no chance of seeing you money like fiat (actual you could see you bitcoin in paper if you convert in in paper wallet, this is closest to the physical form of crypto). There wont be much problem for people once they get used to the concept. there many tokens available with different purpose in purchase.
Once the transaction time is lowered withing minute or so, majority people will find it easy to operate with.