Of course, there are exceptions. But of all the people I know who travel to Scotland on business (railway and otherwise), the sleeper is very much the minority, and that is borne out by CS’s own data on business use.
Anecdotally - obviously - but my employer doesn’t mind, and lets me choose. I day train and hotel, as that works much better for me; I leave work in London normalish time, work on the train for a bit, arrive in Glasgow for a nightcap at the Pot Still, decent nights sleep (impossible for me on the sleeper), up normal time, gym or walk around Glasgow as it wakes up, breakfast, then in the office for 0830. Finish up mid afternoon, on 1538, work for a couple of hours, home by 2100.