There are several services I use which are still cash-only, including the barbers and taxis (mainly because of the extortionate fees involved with processing card payments if you run a small business). I could probably substitute those for similar services which do accept cards, but that would involve leaving providers I trust for someone of unknown quantity or I don't want to use for ethical reasons.
Also, paying by cash in a restaurant, especially when there's a group of you, is so much easier than trying to split a bill and make 10 card payments. Tipping is easier too if you can leave some change on the table rather than having to say how much you want to tip on the card machine, and there's more chance of it actually getting to the staff.
The privacy element of cash is important too. I'm not doing anything dodgy, but I fundamentally dislike companies holding lots of data on my personal spending (and travelling, which is why my travel cards aren't registered). Even if they don't do anything with it, there are far too many cases where companies have been compromised and lost customer data. The less data they have, the less they can lose.
So whilst I could go cashless, I wouldn't want to as it would be inconvenient and involve a reduction in privacy.