As from mendix7 , the platform start usages a serverless architecture, No longer NPE's can just live in the server’s memory ,
what if the next request ended up being served by a different runtime instance? so they had to be included in each request.
You can go through https://docs.mendix.com/refguide/transient-objects-garbage-collecting/#3-client-side-garbage-collection
also there is a old thread about this topic
Hope it helps.