Speaking as a customer (of other trades and shops) a C&P card reader makes life a lot easier (for me anyway!). I'd rather hoik out the old Visa, type in the magic numbers and have everything paid without having to drive to the bank and back with a guesstimated amount of dosh that may not be enough should the job's cost overrun.
Paying by Paypal or mobile (Android Pay/Apple Pay) would be a nice option to have too, but again everything has a price. I don't know what the costs are for e-payments so can't really comment specifically.
From the other side of the fence, card's aren't free to process like cash or cheques (if you don't factor in parking, petrol going to the bank, etc that is). There are ongoing as well as initial costs. It really depends on whether it's worth it to your business or not. If you have a lot of people that ask "can I pay by card?" and it's a pain in the jacksie to get to the bank (i.e. you live in the Highlands like me!) then it'd probably be worthwhile to take cards.
The benefits have to outweigh the costs (not just financial costs but other costs like the time and effort required to get to a bank).
I don't see cash going anywhere anytime soon though and it'll probably remain the preferred payment method for many years to come.