Never just throw out seed on an unprepared surface and expect it to grow, some will, but most won't.
Proper prep is vital to the successful planting of most anything.
It is a good idea to rake little grooves into your prepared seed bed, spread the seed, topdress and then roll with a roller no more than half full with water to press the seed in contact with the soil.
And be patient. A good turfgrass blend will have different seed varieties that will germinate at different rates. Perrenial ryes should pop up within a week where as some bluegrasses and fescues may take 14-21 days.