In many cases we have very detailed data for some places but not for all. We still like to use caches. If we do not want to build very large cache (from data that does not really exists) we need to use the "cache on demand" option that is slow and takes disk space without any control or work dynamic. Why not has an option to get the dynamic data when no cache exists? Dynamic is quick (not as cache but close) and does not create data on disk. It can be done today by programing the client but it is not simple if you have many different clients. A little similar idea is this: https://community.esri.com/ideas/1261