For some houses, you just want to sell quickly to get a profit. If you don't need to do much and can flip for $30K, then good deal.
For some other houses, you want to renovate before sell for a much larger profit.
In my mind, I sell two kind of houses without renovation- the ones that either in very good condition- move in ready, or very poor condition that needs lots of effort.
Otherwise, I do a little and sell for a better price.