You're right about the cashiers though, they're super quick.
The good thing about the card is that you hand it over, and while the reader is talking to the bank you have a few seconds to continue packing your bags. I've simply found it flows better with card every time, as long as you remember which checkout has the dicky card reader that needs 3 tries.
Standard on most bank cards in the UK. No pin or anything. Tap it on the machine and you go. Takes 2 seconds at most.
Still, I do hold cash sometimes, you do need it in some cases.
It's faster, and the app gives a list of the purchases you've made with a card, so I can track what I'm spending relatively easily. Unfortunately, there are still lots of stores that haven't upgraded to contactless yet, which means I can't rely on Android pay for the time being. I can see this being much worse in Europe where contactless payments aren't implemented in many more places than here in Canada.
A) there is a risk as everyone can create a stripe account and buy a charger. Personally I would never notice.
B) every transaction creates costs. Some visible (depit charging fee) some hidden (credit transaction fee)
C) At least in most of Europe it is far from widely supported, even thought it's growing for a while now. Except you stick to the most touristy places that is. In south east Asia I haven't seen it at all except in tourist focused places.
Personally, the convenience of: not having to wear a wallet at all (I just carry the card in my pocket) and not having to deal with coins, negotiate if I'm paying a big bill etc. is just amazing. Even if someone steals $10 from me once in a blue moon, it's well worth it.
The credit card never really saved me. It really just is there to make life a little easier.
When I tried using my debit card and they ended up taking the money and then refunding it over a week later.
[0]: In contrast to e.g. Rewe which is also mostly operated by independent merchants but has strict rules for those.
I've never had to sign in the last couple of years when using my credit card. Fewer smaller shops would take it than in the UK, but otherwise I never noticed any difference.
People pay with rounded bills most of the time, cashiers are fast at returning change (amounts are usually a single cent below the full euro for each item, so change isn't a big problem).
The credit card workflow requires you to sign as well (or alternatively sometimes your pin if it's a debit card). Also, no swiping, only chip readers.
So in essence, taking out the bills is comparable to taking out your card, and the question is whether signing/entering pin is faster than the cashier giving you your change.
Of course occasionally you will pay in exact change, but that's balanced out by all the times you have to insert your card a second time, followed by trying another card.