Yes - if you're playing against 70-80mph bowlers on fast bouncy tracks, its probably necessary.
This is less than 10% of all amateur cricket though. Most amateur cricketers playing against 50-60mph "pace" bowlers on puddings where a bouncer reaches them at 40mph if at all, don't even really need a helmet, let alone thigh guard, chest guard, arm guard, lol.
This might be correct , but IMO, the idea of wearing protection is to mitigate the possibility of an Injury. Even at 40 Mph, if you get hit on your head , or your hip bone, it's gonna hurt for some time . And a ball hitting on thigh pad gives you a chance to get some runs too .
I play at a pretty low level now where bowlers are mostly in the 50 -70 MPH region and wear all the necessary protection while batting and was once was hit on my helmet by a ball that rose sharply from short of length of a bowler who was probably bowling around 50- 60 mph. Felt fine after sitting for a few minutes and came back to bat . It was only the second day that I had concussion symptoms . Had to take the day off from office . Without a helmet that could had been a dangerous situation .
There are many in my team who play without thigh pads and time and again I have seen them getting hit on their hip joint and being unable to continue their innings . One guy lost his tooth while trying to sweep a spinner without helmet on .This prompted our league to make helmets mandatory.
Everyone has their own preferences, but i think it's better to be wearing protective equipment which ever level a person is playing cricket at.