In the Netscape server the corresponding per-user threads use considerable resources. And lord help you if you do enough fetches by message-id to cause the history file to get mapped in. The additional state we're adding here isn't significant. Actually executing the searches and maintaining the full-text indexes both dwarf the resource requirements of keeping this state. And these are just the price that has to be paid to support real full-text searching.
Clients currently know how to read groups.
So once they get the name of the search result group, they don't have to do anything new to display the results. It's just not as good as the alternative.