NATO is a military alliance not a charity.
Eastern european countries were accepted only because they served the West's plan to increase their geopolitical weight and surround Russia:
Internal NATO reaction to these former
Warsaw Pact countries was initially negative, but by the
1991 Rome summit in November, members agreed to a series of goals that could lead to accession, such as market and democratic liberalization, and that NATO should be a partner in these efforts. Debate within the American government as to whether enlargement of NATO was feasible or desirable began during the
George H.W. Bush administration. By mid-1992,
a consensus emerged within the administration that NATO enlargement was a wise realpolitik measure to strengthen Euro-American hegemony. In the absence of NATO enlargement, Bush administration officials worried that the European Union might fill the security vacuum in
Central Europe, and thus challenge American post-Cold War influence.
Enlargement of NATO - Wikipedia
Because Russia dismantled the Cold War security structure of the Soviet Union in good faith only to get vindictiveness, Cold War revanchism, NATO expansion in return.
This guy invaded Grenada, supported coups, financed invasions and bloody proxy wars throughout Central America so that America's neighbors didn't have soviet weapons, missiles on her borders despite her huge nuclear arsenal: