Well the alternative is propping up the high-paying jobs using subsidies and shutting out competition, which isn't exactly a winning long-term strategy. The high-paying jobs aren't going to stick around unless you force them to with some kind of jobs program which is just taxing everyone else so that this small, select group of people can benefit; why shouldn't everyone get a cushy do-nothing job at taxpayer expense? Clearly, that isn't sustainable or fair.
The UBI lets everyone in society have a safety net so they can go looking for another high-paying job, or get an education in another field to get a new high-paying job.
That and the wish for a stable society- not some aristocratic mess reminding of the late Roman empire, so ready for a final civil war as show down, that its rulers rather collapse the whole problem outwards.