Traditionally, in the West, the Church ran charities to help the poor. Tithing and charitable giving contributed to the coffers managed by, say, local monasteries. Communities also helped each other out on an as-needed basis, In both cases, help was local and this meant insight into the particular situation of each person who needed it (hence the superiority of the principle of subsidiarity). In both cases, no politicians were involved.
In the West, with the kicking out of the Church from the public sphere and the rise of hyperindividualism, many of the good works performed by the Church and the community was arrogated by the State. The State is now the uncontested institution, it is now the Church. Now these things become subject to and embroiled in all sorts considerations unrelated to the basic problem of dealing with someone in need. UBI entrenches the very isolating hyperindividualism that ruined the family and destroyed the resulting communities.
That is the problem today, but we could also just have it be based on filed income and get rid of the bureaucracy instead. The issue is that some political parties are actively against helping the poor. The more practical idea is a universal poor stipend. The problem with UBI is that it would literally require everyone above income X to pay and extra $500/month in taxes just so they could receive a "free" $500/month in taxes.
You also get the instinct to “parent” the poor and limit what they can buy.
Giving it to everyone isn’t the best idea but it’s the best way to keep politicians out of the kitchen.
(And I say this as someone who’s against the idea. But I do think the “universal” is the best idea within a bad idea.)