More and more tyres are tubeless compatible (or tubeless ready, which I understand is technically not the same thing, though I can't remember the details) so new tyres aren't really the problem, it's the rims.
Even if the rims are OK, to convert you need to invest in valves, sealant and probably rim tape.
I have 2 bikes that are be ready to go, aside from buying sealant, as they are already taped, I have valves, and the tyres are tubeless compatible, but i just can’t bring myself to do it. Fear of sealant mess over bike and clothes is holding me back.
As a slight aside, most tubeless ready / compatible tyres are heavier than their non-tubeless equivalents, and as they become more common I suppose many people who don’t want to go tubeless will end up riding tubeless tyres but with tubes in - a heavier combination that is necessary.