Historically drivers and agencies both benefitted from the Ltd Co. arrangements - drivers took home more as they could claim travel, subsistence and various other expenses (= more take home pay) and the agencies avoided the expensive on-costs associated with PAYE employment.
The criteria for whether or not it was/is legit hasn’t changed, but who HMRC can pursue in the event that they deem it to be false self-employment has. In the past, if there was a ‘debt’ accrued to HMRC, the company would fold and HMRC would get nothing/very little. Now, the agency and the company they drive for can be pursued by HMRC so many companies are ‘playing it safe’ by insisting on PAYE either direct or via Umbrella.
Some people will have been duped/coerced into going down the Ltd Co route, others will have gone into it with open eyes. Doesn’t seem right for the latter to start claiming through the courts.