As explained superbly in
(list) list is executed in a subshell environment (see COMMAND EXECU-
TION ENVIRONMENT below). Variable assignments and builtin com-
mands that affect the shell's environment do not remain in
effect after the command completes. The return status is the
exit status of list.
In other words, this is a handy way to do something somewhere else without having to go there and coming back.