In what circunstances the investiment tool worth?

Today I spent 5 credits to invest 40kkk. To profit only 1kkk in the end.
What's the purpose for this tool? Since the profit is so low.

So why are u investing so low amount of money? Also u can try to take district to have +14%

The more cash you have, the better the invest will be...Imagine a lot of players have muuuch more than 40kkk, at least 20 times more, so the profit will be very good, especially if you use items for invest or even take streets for the district.

Thanks for the answers guys. I guess I didn't know it was even possible to get that much of money.