How often do people fly SVFR?
From my experience in the US at the facilities I've worked, and the discussions I've had with other controllers, it depends heavily on the area's weather patterns. The facilities I've worked, it's been usually a tool, when people are trying to get in right before the weather hits, or they're seeing good improvement in neighboring airports and at the main one, and know that it'll be good enough to make it between the two areas.

Other places, like coastal or areas where fog banks are common, SVFR can be useful, esp if only half the field is covered in clouds, and you need to make it in or can easily get out.

Personally, I'd probably just file IFR and cancel when I got to a good spot VFR, if I just wanted to go out and enjoy, versus just flying to a destination. 

Also, note, SVFR in terms of separation is only one SVFR aircraft(and really aircraft period) in the airspace at a time. So, you'll be delayed to come in if there's IFR, or other SVFR aircraft ahead of you.

Helicopters generally do request it more than fixed wing aircraft in my experience. Also, realize a pilot has to explicitly request SVFR, a controller can't prompt or hint at the correct terminology to use to request like saying "Do you have a SPECIAL request"