Big exchanges don’t list coins/tokens easy , it actually costs a lot
For example Binance asked the founder of Digibyte around a 500,000 USD to list DGB , that was for long a heated debate on twitter to follow between CZ (Binance) and Jarod Tate (DGB)
But not all exchanges ask FIAT , some ask a % of the total supply of a coin/token …
And some older tokens/coins well those do get listed for free for obvious reasons.
Exchanges aren’t charities
Quote from another crypto forum - If you are looking to list your coin on an exchange, expect to pay: $6,000-$30,000 for listing on a small exchange. $60,000-$300,000 for listing on a medium-sized exchange. $1M -$2.5M for listing on a high-volume exchange.