In an ideal world, there would be no welfare whatsoever. However, in the US I do think that UBI is a more reasonable path forward than continuing the current welfare system. Currently the US has probably thousands of different welfare programs, each with tons of overhead. Better to just mail everyone a check. It also significantly improves incentives, for example fixing the issue you mentioned of people getting trapped in welfare. According to Charles Murray's In Our Hands, $13k/year would be cheaper than the existing welfare system. Here's an interview with Murray.

However, I only consider it acceptable if it replaces all other welfare, including heath-care-related welfare, and I suspect that this will never be politically possible. I'd also like it to result in an elimination of all work-related regulations such as minimum wage, since with UBI there should be no excuse that people are being forced to work and therefore the government needs to protect them.