Well one great grandad was born in 1895 and he was an electrical fitter in the 1911 census, his dad, my gg grandad was born 1876, so again age is fine and he was a musician, i can't see that being a reason to not go.
The other side, my great grandad was born 1901, and was a painter and decorator and his dad was born 1874, he was a coal miner.
One guy is too old by the start of WWI, and another is a farmer born in 1879.
thing is maybe all these men did have bad eyesight or ill health but their brothers and sons didn't go either, i have to go into '3x removed cousins' territory to find anyone that was involved!
So strange!