Plenty of people only have 2-4GB of RAM, and Slack eating up 360MB along with a couple other bloated apps and some God-foresaken autoplaying video ad can easily start requiring swapping and slow a computer to a crawl.
Sure, people could spend more money to mostly sidestep the issue (supposing they didn't have any workloads which actually benefited from all available RAM), but that doesn't make it a non-issue.