European kilt wearers as well as other men without Scottish roots will mostly consider the kilt casual wear; that means for relaxing at home in the evening, during weekends and when on holiday.
   Doing shopping, going sightseeing, hiking and eating at informal restaurants are other situations where they from time to time should like to wear their kilt.
   Dressed up with a suitable jacket some of them might also go kilted to the theatre or opera house, but contrary to Scotsmen and men with Scottish roots they should hardly use a kilt for weddings or parties calling for a tuxedo or similar.
   Also it is not very likely that they would think of wearing a kilt to job, at least not on a regular basis.
 

To most European and other non-Scottish kilt wearers the kilt is simply a valuable addition to their wardrobe, rather than a more general substitute to trousers.

Accordingly European men might very well recognize and appreciate the craftsmanship put into an expensive hand made kilt, however prefer to buy a more versatile and cheaper casual tartan kilt or a solid coloured modern kilt, these being more than adequate for the functions where they will be wearing a kilt.
   That also implies that we here should talk the kilt itself rather than highland attire.
   The various types of kilt shall be described later on.

I have always liked wearing shorts and have done it a lot. Now the kilt has to a great extend replaced my shorts wearing, the kilt being even more comfortable and more versatile.

What about...?
The inevitable question, of course. Well, some do always, some do from time to time, and some never do. Without doubt every kilt wearer has at leat once tried how it feels like. Was the answer usefull? 
No, and it wasn't intended to be.
   What you do or do not have under your kilt is totally private business. The curiosity whether true or not may be the reason that only the kilt has survived as a manly skirted garment. Accordingly we better keep the secret very much alive.