Care to elaborate? I can think of many reasons why it is a good security measure to have it disabled...
Search path-mtu discovery for more.
I have seen ICMP being used as a tunnel for a remote shell plenty of times. Network admins just see the traffic as harmless ping and ignore it.
I didn't say allow ICMP (echo) through your firewall, just respond to an echo from the external interface. Blocking echo responses does not stop malicious people finding your device. Just look at nmap for two minutes, you can SYN scan a subnet in a few minutes and find all the hosts that are connected even when they don't respond to ICMP ECHO packets.
ICMP ECHO is extremely useful for diagnostics, not least the thinkbroadband BQM
plusnet unlimited fibre
80/20 since 2 Jun 14 / Sync 6th Nov: 58,280/10,784 kbps with G.INP
16 years UK broadband (Since 1999 ntl:cable trial), Asus RT-AC68U & HG612 - BQM - Flash Speedtest - HTML Speedtest