The correct discipline have always been to purchase coins or consolidate small units of coins eg. BTC on CEX until it's big enough to pay transaction fee for it and send it to a decentralized wallet for preservation and the correct slogan I've always known is "Not your keys, Not your coin".
Be Warned and Be Wise while making a decision on wallet to preserve your coins.
Even with this idea of having to store your coins on centralized exchanges until they are big enough to pay fees on them and have them transferred to a decentralized wallet doesn’t work. I say this because, the movement it’s big enough or close to that, you’re already taking a risk you wouldn’t have liked to take.
Also, it’s easier to save little or small amounts on decentralized exchanges than centralized exchanges. Centralized exchanges have deposit limits of which, should you happen to send coins below that defined limit, the coin is lost to you. In the case of decentralized exchange, there is no limit what so ever. You just be cool with the fees which is usually far less than what centralized exchanges would require of you.
Reasons far from storage would account for users having to have their coins on centralized exchanges. Maybe for trading, swap for other coins or exchange for fiat and not storage, that would be so wrong.