Smallaxe - I totally agree. A common thing I see when homeowners do their own leaves is a very clumpy growth habit to their lawn. What happens is leaves settle and stick to any bare spots, suffocating the lawn there and increasing the size of the bare spots. This perpetuates the cycle. Couple that with the grass getting long and laying over and choking itself out and you can destroy a nice lawn in no time.
Trying to renovate this kind of lawn can also be difficult because a slit seeder doesn't get into the hollows very well, so you almost need to topdress the whole lawn. I had a lawn like this that I renovated only to have it return to it's clumpy growth habit. The customer was doing the mowing and cleanups themself. It was only after making multiple follow-up visits did I realize they were letting the leaves sit for extended periods and mowing high with a mulching mower, which never stood the grass up.