What is wrong with a snokel I reckon they are great

I  can understand in some situations a snorkel can be a hindrance. For 
example I have dived sinkholes in the Nullabore and yes a snorkel
supposedly 
was  a catch hazard ( I will never do it again it scared the **** out of
me 
and if you want to do this for fun good on you ) and the same applies to 
penetrating wrecks.

However for normal diving isn't a snorkel a good thing