Fun fact: Poland literally begged for that on their knees, offering all manners of vassal pledges in exchange, for nearly 30 years. It's been finally graciously granted by the sovereign in 2019, but it's only on 90 days and you must still get permit in ESTA (which you basically can't get if you were ever convicted or for many other reasons).
Money or idealism (look what it did to mfers). Though usually not even that big money. If you look at polish political class formed by former opposition and opportunists, a lot of them advanced materially very much, though actually rarily to the real bourgeoisie, more to the grant-paid traitor scum territory, and the idealist opposition leaders got fucked up into the freak show veterans cathegory.
Yeah i know. Really ironic, they can still refuse them based on a whim, and i bet diamonds against nuts that some countries are getting much higher ratio of refusals than some others.