Yes, viruses on mobile phones are quite rare, but as they say, installing an antivirus will not be superfluous.
Worry about the safe use of a smartphone is never superfluous. Will the virus get on the smartphone or not, we can not know, but it is better to have an antivirus program at hand.
The techologe developes very quickly. Now a lot of smart phones use for the payment. And if there ara viruses in smartfone I do not know how the safe will be the paymants. So for smartfones antiviruses are neccessary now.
You're right. Already many services accept contactless payment, which can be done with the help of smartphones.
So without antiviruses can not do.