Eh, that's not really an issue for me. But I've been in freeform or 'rules light' games before, and found that without a system to regulate things, it tends to either go downhill fast, or I end up writing 500-1000 word essays on my character's abilities, just so me, the DM, and the other players are on the same page. Especially in superhero games, where there's been times where I list 'cold control', and then have to explicitly say that I can freeze things other than water, or that I can lower the temperature to X degrees, and so on. A system eliminates that confusion, so everyone knows what is going on.