While true - ICMP is a ubiquitous protocol used all over the internet, but computers and network devices a like.
It also often gets overlooked, so while "you can tunnel inside almost any protocol", it is very common for malware to use ICMP for C&C.
This isn't to say ICMP should be blocked completely. But limiting the size and the value of the payload in ICMP ECHO requests and replies can definitely help.