As can be seen from other comments, people tend to focus on the consistency implications, but something not discussed often in the context of distributed systems is that caches tend to introduce bimodality and metastability [0] [1].
See e.g. DynamoDB for an example of design taking it into account [2].
[0] https://brooker.co.za/blog/2021/08/27/caches.html
[1] https://sigops.org/s/conferences/hotos/2021/papers/hotos21-s...