I think the FCC said it best…
In addition to violating Commission rules, linking repeaters is not in the public interest. Because GMRS spectrum is limited and used on a shared “commons” basis, the service only works well on a localized basis when users can hear each other and cooperate in the sharing of channels. Linking repeaters not only increases the potential for interference, but also uses up a limited spectrum resource over much larger areas than intended, limiting localized availability of the repeater channels.
GMRS and the Family Radio Service (FRS), which share many of the GMRS channels, are intended for individuals such as family members and friends, scouting troops, emergency response groups, and hobbyists to communicate with each other over short distances, directly or through a repeater station. Linking repeaters, via the internet or other networks, undermines the purpose and usefulness of the GMRS and FRS.