Ok, when I was at nationals in July here are soem example of what I saw. The lead leg side kick (or cut kick) used primarily in combination to set up single or double roundhouses. Since a point was coming off of two ro three kicks...hard to say if it was the cut kick or the follow ups that scored. Nonetheless, the kicks were and are used.
In one memorbale match amongst the younger mid-levle color belts (blue belts i believe). One young girl had her first opponent timed. Everytime they tried to open with a roundhouse kick, she'd throw a wickedly fast back kick counter...her opponent never adjusted and she was quickly gapped (matched stopped due to seven point score differnce). However, in a later match her other oppoenent was ready for her and would set ehr up to throw that back kick and hen stuff it with a cut kick (read fast side kick) and the score on the follow up.
In another case, I saw a great combination in which a teen amle competitor drove his opponenet back to the edge of the ring with a flurry of fast strong roundhous kicks than knocked him out of the ring with a strong sliding side kick. Scored 2 or 3 points on the exchange.
This is at a recent national level competition. It's, I think, a place where one will get agood sample of what WTF tkd schools are doing as far as competition tactics and strategy is concerned. I saw plenty of coaches drilling cut kicks. they wouldn't waste the time if the techniue was not being scored or if it was not useful..especially at this level of competition.
True, the proportion of sidekicks compared to the roundhouse is very low. 90% of your kicks will be some version of a roundhouse. Bu the lead leg side kick, front push kick, axe/xresent kick, back kick and hook kick stil regulalry make appearances...and score or set up scoring opportunities. I've never seen at that level or at the local level in my part of the country where judges have been told NOT to score these kicks. I'm not saying that this ahs not happened elsewhere...just not at nationals or in myneck of the woods.
Peace,
Erik