I met an American woman who lived in the UK for ten+ years during her childhood, and then when she was 17 her parents had moved back to the US. She, like them, had ILR. She went to the US for the last year of high school and then college. She didn't return to Britain for two years, and when she did, the IO didn't believe she was returning to "resume her residence", and cancelled her ILR.
I know that she could have applied to resume her residence, but she didn't. She just took a chance and lost BIG.
I believe in these circumstances it would have been possible to appeal the cancellation of ILR, but she didn't and so she is just an American with a British accent...
Just one example of why it's a good idea to go for naturalisation.
Another is: You can vote and your name is on the electoral rolls - important for all kinds of reasons.