You have to differentiate between two types of server side blocks. One are blocks that receive variables from the server to use in their registerBlockType function and the others are blocks that are created entirely by the server through a php function. The latter is called server side rendered blocks.
In my opinion this functionality is very good for people who are still not used to the world of Gutenberg blocks. In addition, this feature is also good for those who have not yet arrived in the world of REST APIs or can not free themselves from php functions. I have not had any function what else you could use the Serverside Rendered Blocks for. If anything else turns out, I will write it down. More information about Dynamic Blocks is available on the official WordPress documentation page: