For example, are there places that accept payments with altcoins? Or is it just used to convert bitcoin?
Suppose you launched your altcoin , if people will use your coin more and more then you will get profit of transactions charges which has been deduced from the account of the altcoin user . In this way you can make unlimited profit but condition is that your coin should be use as much as possible .
Here is no doubt that altcoin have much advantage for the bicoiners and I think most of the bitcoiners are making profit in legit way only through the altcoin investment ( which us know as trading ) .