If you compare the 'entry level' components to high-end components of the same brand, the main difference is usually that the higher end components, due to their tighter manufacturing tolerances and better materials, will last longer and stay in adjustment better and provide cleaner shifting over time and heavy use.
Generally the higher end parts that more avid/higher mileage cyclists prefer are the ones that are built for more speeds - I think the top end stuff is at 12 speed cassettes now - that lower end stuff. So if you want a good quality bike that runs smoothly for many seasons, you get a higher number of speeds.
If you want to save dough and get a cheaper or older bike, they come with less speeds - my most modern bike has a 10 speed cassette, but I have 9, 8, 7 and 6 speed bikes still hanging around.
There are likely still folks who prefer fewer speeds, and the price for low-end new stuff is pretty close to higher end used stuff from years ago, so many are happy riding older the top-of-the-range 8 and 9 speeds rather than entry level 8 or 9 speeds.