The galaxy is gi-normous
! Assume for a moment that the Federation, Romulans, Klingons, Ferengi, Cardassians, Shelliak, Orions First Federation and Breen contained five thousand star systems each
. That is nine thousand. Double it. Round up. Twenty thousand star systems. This in a galaxy with something like four hundred billion stars
in it. Assume all the Alpha Quadrant powers make up one percent of known and explored space. Just one percent. That means the Federation has pretty mapped out two million star systems--less than one half of one percent
of the galaxy.
see zero problems about further exploration.
I know how big the real galaxy is but,
they designated how far who goes where. Space filled up quick after all those series. I guess you can take it as the "faster than warp species" out of the galaxy.