Just curious as to peoples opinions on staking systems.

So much talk of using staking systems, but at the same time negative comments about winning on such games as roulette.

What is the purpose of a staking system?
I believe that it is to increase profits. eg instead of returning 102% with a straight bet, using a staking system to increase the return to say, 110%.
If this is possible, why not changing a 97.3% return on roulette to over 100% return?

Just looking for peoples opinions...