Comment by avianlyric

The size of an ACK is minuscule (40 bytes) compared to any reasonable packet size (usually around 1400 bytes).

In most client situations where you have high down bandwidth, but limited up, that suggests the vast majority of data is heading towards the client, and client isn’t sending much outbound. In which case your client may end up delaying every ACK to maximum timeout, simply because it doesn’t often send reply data in response to a server response.

HTTP is clear example of this. Client issues a request to the server, server replies. Client accepts rely, but never sends any further data to the server. In this case, delaying the client ACK is just a waste of time.