Lugs look cool. You said it yourself: "...on very lovely high end frames".

There was a time when the best tubing available for bikes had to be lugged. Or fillet brazed. That caliber of tubing was far too thin to be "welded".

Nowadays, awesome frames can be TIG welded, brazed, lugged. Aluminum frames are typically TIG welded because it can be done by machine. Same for the thicker tubing used on motorcycles.

Newer steel alloys allow lugs, brazing, and TIG welding. It's all up to the builder and the buyer.

Glues have been used in the past and I believe that's how carbon fiber bikes are held together. Brazing is just another name for gluing tubes together except it's either brass or silver that acts as the glue. Not sure why they don't use glues today except maybe they don't work too well.