Define "advantage" and by who is benefiting from it. One community wants some new buzz with each market cycle. Some want their egos stroked at the start of group rides, with the bike they are on. Factories care about time to complete the build VS the cost to do so. Pick your poison.

Lugs provide a very well established method to support and help position the tubes during the build, provide massive surface area at the joint to allow non welding joining methods be strong enough.

Back when bicycles were considered the height of modern industrial ability (late 1800s) brazing was the usual way to join steel tubes. Welding wasn't anywhere near as "refined" as these days, both tube alloys (as example 531 came about in the 1930s and wasn't considered a weldable alloy then) and filler rods weren't what they are today. So steel structures were often brazed. Fillet brazed joints didn't offer much branding and took some skill and time to look nice. Lugs offered a lot of visual details for branding and worked well for a factory production and cost reduction of joining when done in volume. Over the decades since consumer acceptance has swung from fillet to lugs to welding and now composites with their shapes determined by a mold.

There have been a few published efforts to test different joining methods (of steel tubes) in the last few decades. Bicycling magazine had an article where the commissioned 3 different joining methods and tested the strengths and failure modes (for steel tubes). The 3 joints were lugged, filleted and welded. The failure modes were somewhat different but they all did fail. They all were good enough to work too. Some of this was about where along the tube, from the joint, the HAZ was as this is where the tube strength suffered. Also undercutting, be it from poor welding or heavy filing could come into play. Lugs can hide best mitering and thus become a structural member instead of a filler housing.

Their conclusion was that all 3 methods worked well if done well, could fail is not done well or if the stresses exceeded the designs.

One limiting aspect of lugged use in the last 3 decades, or so, has been the use of more tube diameters and a greater range of tube angles. producing enough lugs at a low enough cost to fit all the geometry and tube size choices has a very high cost. So lug offerings have become fewer, basic economics at play. It is these reasons that some, like me who don't weld, have gone to fillets for much of their work. Yet half the half dozen frames I have built in the last few years have been with self made lugs. Andy