Staking service or staking pool has happened from many years ago until today, only PoS based project can do that.
If I can afford to hold it by myself, I would rather stake it on my own VPS other than giving it to the exchange.
But if you do not know how to do it or do not want to keep maintain it, giving it to the service provider is fine too.
This is not interest buy staking the coin to get a new coin because of proof of stake consensus.
As i remember DASH required 1000 DASH coin to start a masternode and staking it t ,you can earn around 7% anually.its impossible for lower budget traders to have that amount unless you have a large fund willing to invest.
The problem of giving it to 3rd party is the risk that you will lost what you invest for staking since you dont have full control of your balance.