Under capitalism, UBI is the destruction of the welfare state. This is why Hayek liked the idea. It will remove the notion of guaranteed services and make things like healthcare and retirement a function of "the market", so e.g. where before you were guaranteed a trip to the doctor, now you have to decide whether you can afford it. A middleman has been created between you and the service: a limited amount of funds. Inflation could wipe you out. The government can lag behind on increasing it, just like they do with the minimum wage. Finance could take over and jack up prices like it does with housing.

At the same time, consider the origins and nature of the welfare state itself: as a mollifying policy to prevent socialists from gaining power. There was no long-running campaign by Socdems to create the welfare state in most countries where it emerged. Instead, it appeared where there were mass anti-government movements (the United States, the UK, Canada) or where it was externally installed as part of an anticommunist bulwark (Western Europe). That pressure no longer exists in those countries. The left is almost nonexistent in these places. The welfare state is therefore not maintained by them - it is maintained by liberals that view these things as normalized entitlements. Therefore, they are susceptible to the neoliberalism that gladly vampirizes state programs through privatization. It will continue to happen until the left returns.

Here's to hoping the next time we actually do take power so that we can permanently guarantee services