I'm in the NO camp here.
Several reasons. There are areas in the country where the market is completely different. Cornwall has always been populated by general tradesmen. OK there are the specialists but there isn't the same market for specialists as there is in other parts of the country. A lot of tradesmen in this part of the world have one main trade and can diversify into other trades.
A good plumber may learn to do basic tiling. None of the bathrooms I get asked to do are anything special. The biggest challenge I've had is that wetroom TBH - photos in my profile.
To licence trades individually would put the likes of me out of business. I'm considered perfectly capable of doing what I do. I have a strong and loyal customer base.
If tiling gets licenced, then what about plastering? How many of us have rendered/skimmed a wall in preparation for tiling? What about dry lining? How does the client know that we know what length screws to use in the wall - where will it all stop.
If we MUST regulate the industry, I think tiling is one such trade where tilers should be assessed on their competence. I would suggest that the industry promotes a benchmark, which tilers can set out to achieve if they so wish. This way someone looking for a tiler can if they wish, insist that the tiler has achieved this, but the absence of this 'qualification' would not prohibit someone from tiling for a living.
If this were in place I would expect customers to ask for this if they have a marble floor to go down, but maybe not insist if they just want a kitchen splashback in 6x6.
It is also my belief that the government have had too much opportunity to screw up trade
regulations. Don't even get me started on NICEIC