Caveat: there are a lot of non-ISP entities in that diagram, and they are often more motivated by control and political power than direct profit. But, I'm going to assume you really do mean ISPs.

The answer:

ISPs are driven by profit and the need to provide acceptable service to their customers.

"Acceptable" being defined as "enough so that they don't quit being customers".

Sometimes, an upstart ISP will show up and offer exceptional service at remarkable rates. However, they often fail, run out of funds, or are acquired by an equity firm or a larger ISP. At that point, their focus is shifted back to profit and delivering only acceptable service.