If you do a lot of business in Turkey you might want to make sure that you don't have to wait for a lengthy visa process, or any other diplomatic issues that might come. Being able to travel into a country as a citizen has a lot of benefits, and rights.
Not all rich people live in Europe or the US. If you live in Middle East or an African country, being able to move without hassle to a safer country in case of social unrest (just think about Turkey's neighbors: Syria, Iraq, Iran...) may be of great value.
Plus at least until recently Turkeys economy was growing steadily so it was an interesting place for doing business.
Wishful thinking?
Potentially a future EU member?
Ha. In like 20-30 years, assuming that the entire political course of the country does a 180 degree spin and stays on it. It would be faster, cheaper, and easier, to just live in any EU country for 5 years and get the passport that way.
Don't see that happening anytime soon, with how things are going right now.