Even though my computer can run all applications without a hitch, it is still very wasteful to constantly use CPU power because of technology choices or plain laziness. As an example, Spotify and Slack are two applications that seem to use most of my CPU after Chrome. Spotify and Slack combined seems to hover around 5-15% of total CPU (a two year old i7). When there is a lot of traffic in Slack I have seen it using 15-20% by itself, with multiple processes running and memory use going above 200 megs.
Both applications work smoothly, but should they really use that much resources? A chat application? A music player? With modern CPU's I would expect them to be at the bottom of the process list when sorted by CPU usage. I used IRC on my Pentium 75Mhz and it ran fine. When simple applications are made so poorly that they use that much resources, what is the worldwide impact of that power use? And what about the users that don't have powerful and expensive CPU's?