These are assuming a a paid installation.
Strangely enough if you change the question to percentages who do that after doing it themselves with seed from a jug, on top of barricading off the area, making a special phone call or email to let you know, etc. You get
Percent that expects warranty after not watering, 90%
Percent that think all seed is alike, 99%
Percent that think you can grow grass in the densest of shade and poorest of soils because it says Dense Shade Mix on the Label, 100%
Percent of people who refuse to prune trees to let in light, but expect a lawn in their shade exactly like the sunny areas of the neighbor, and assume because they hire out services that this is not a problem under a reasonable budget. 99%
Percentage of statistics that are made up on the spot when talking percentages 90%