The honest answer
Strictly, no. Most massage in the UK happens in your underwear, with a towel over whatever isn't being worked on, and plenty of it is very good. I'd never call it a lesser treatment.
But I've had massage both ways over the years, and I don't think they're the same treatment. With nothing on it's more sensory, more continuous, and in one or two places more thorough. So my answer is: necessary, no. Better, I believe, yes.
Mr Knight
I found this out in my twenties. I had a bad back and went to see a chap called Mr Knight about it. He left me in the room to get undressed, so I stripped down to my underwear and stood there waiting for him to come back. When he came in, he pointed at them and said, “Those will probably get covered in oil. I can tuck a towel into them, or you can take them off. Totally up to you.”
I took them off without a second thought. He was the therapist after all, and I'd come to him with a problem, so I trusted his judgement. And ever since that first enjoyable experience, I've questioned why we cover up for massage. Standing naked, getting ready for my first massage this way, I felt exposed at first. That soon went, and it ended up feeling liberating. It seemed to me Mr Knight understood how a proper massage should be given, and he'd been massaging for 60 years, so I respected his view. And strangely enough, I felt more at ease starkers than I have in most massage clinics. To me, being covered up has always felt clinical and detached. Maybe that's just me.
And lying there with nothing on, the massage felt wonderful. Clean and clear is the best way I can put it. He was 84 and his hands were like sandpaper, but the treatment was completely professional, and after a while I relaxed in a way I hadn't expected to. I think that's what got me into massage in the first place.
There's a longer version of this story on the blog.
The glutes
This is the specific one for me. Your underwear sits exactly where the most neglected muscles are. Keep it on and the glutes are either left out altogether or pressed briefly through the fabric. Yet they're among the biggest muscles we have. They do the sitting and the driving, they hold a surprising amount of tension, and they run straight into the lower back and hips, which is where most people tell me they ache.
Massaged with nothing in the way, they're oiled and treated like any other muscle group, and a stroke can run from the back of the leg up through them into the lower back without stopping at a waistband. I'll say it plainly, because it's half the reason this page exists: there's nothing in a massage quite like having your glutes properly worked.
How it works at The Workshop
We're a naturist spa in Royston, North Hertfordshire, so the question never comes up here. You're naked for your treatment and so is your therapist, the rooms are kept warm, and the massage covers the whole body as one continuous piece. That's rather the point of the naturist massage.
If it's the nudity itself you're unsure about, that's normal, and it settles faster than anyone expects. Most people stop thinking about it a few minutes in.