Newer washing machines vary in time depending on how dirty your clothes are. So the same program may take 50 minutes or 90 minutes. This cannot be solved with a regular timer.
If you have a job with varying hours, you might want to start the washing mashine when you’re heading home. Then you’re clothes are ready to be hung as you arrive and they aren’t laying around for hours.
If you own photovoltaic, you might want to time energy intense home appliances such as washing machines, dish washers etc. to a period of overproduction.
Not saying, these issues are super important but there definitely are use cases for smart devices. However, I’d always recommend using a local / self-hosted rather than a cloud-based solution.