the risk with a hernia, for whoever asked, it that you can get a strangulated hernia, basically a bit of bowel or intestine can go through the small gap and then get stuck and maybe twisted.
its easy to see and check for tho and fairly rare, with my ds2 when he lies down you can press the hernia and it will go flat and 'pop' back in, if however the area ever goes red, inflamed or is painful or the hernia wont go back in then your best bet (the hospital told us) is to go straight to a&e where they could diagnosis and would operate immediately.
because of the fact that is is rare to get the strangulated hernia and as our son isnt bothered we havent had his operated on tho they will do it on the nhs for cosmetic reasons and offered my ds2 the operation on this basis. we politely declined, but if of course he ever had any problems we woudl take him to get it checked out. thankfully so far he never has and as he had got older and his stomach muscles stronger the hernia has reduced, tho he still has an outy belly button and you can 'feel' the hole if you feel around his belly button, but it isnt as big as it was.
i just dont see the point in putting him through an operation unless he needs it or chooses himself to do so.
we had a similar choice with our eldest who has an unusual birth mark on his head, it gives him a bald patch and again the nhs will operate partly because statistically it gives him a miniscule extra risk of skin cancer (on the birht mark itself) but mainly for cosmetic reasons, they would remove it in stages and pull the skin around it tight so that he would end up with a fine line of a scar instead of a bald patch. but tbh he has his hair long and so you cant see it and again he isnt bothered. we opted to wait and see, and if when he is older (he is now 12) he wants the operation then we would ask for it to be done, ditto with ds2 and his belly button.
to us these little quirks of nature are part of them, they dont cause them any harm or suffering so we see no reason to have the operations, if they of course choose to, then that is their choice.