For example, let's say you have a mix of 90% fake likes, and 10% real/organic likes, presumable because they saw your page, saw all of the likes, and thought, "I want to be in on this."
Now, let's say that I post something, and chances are that it's only going to be seen by 100 people. This means that whatever I post will be put in front of 90 garbage accounts and in front of only 10 people who I actually want to target. Unfortunately I can't target based on fake vs. organic accounts.
If I want to increase that 10ppl number, then I'll have to pay more to increase the visibility across the entire population. Let's say I pay $10 to get 200 people to see what I've posted, then 180 fake accounts see it, and only 20 real/organic people see it.
Unsuspecting businesses of any kind, and especially small ones, can't afford to waste money on this kind of mess.