Still most of the crypto wallets has its own exchange where one can do trading or exchange.
You are thinking either of multi-currency wallets or custodial clients. And those exchange features that are supported by such wallets, aren't usually natively developed by them. It's part of a partnership with a 3rd-party. The two most popular bitcoin wallets, Bitcoin Core and Electrum don't have internal exchanges, for example.
It's interesting that Electrum doesn't even have a donation address. Not one that I am familiar with at least. The wallet's developer, ThomasV suggested a long time ago they don't request donations, and suggested to donate to those operating Electrum servers instead.
Thank you for your support. I usually do not request donations for myself, because I do not think it is an effective way to incentivise free software.
Developers who request bounties tend to finish projects quickly, and do not really care about long-term maintenance.
However, you you can donate to the people who run public Electrum servers.
Electrum does relies on servers, and we currently lack an effective way to reward the server operators.
Also note that I created a company that will distribute Electrum, sell paying services to Electrum users, and fund further development of the Electrum software.
On the other hand, Bitcoin Core's
donation address has received over 13 BTC in donations in the last 2 years alone in over 1000 transactions.