And the official signs are not recognised by many, anyway (the one in the link is 'Warning: boobs in road', in case you were wondering).
Can't see how lawyers benefit from fewer signs. You'd be hard pressed to get a case going because a sign had been removed, unless it was to warn of something which no reasonable driver could have anticipated and the accident occurred in direct consequence of the absence. But that's not what the minister means; it's the useless or unnecessary 'informatory' signs that are the problem.
The 'bottom feeders' flourish because of 'no win, no fee'. Legal aid was scrapped for personal injury claims. To entice lawyers to take up this work, the government agreed that they should get a massive uplift in the costs they could claim if successful. Before,the potential claimant had his case scrutinised, the solicitor could be at some risk if he certified a case as deserving support when that proved to be unmerited, and costs were tightly controlled. Cases that didn't get legal aid on the grounds that the case didn't merit it could be appealed to a tribunal, but the tribunal were a pretty tough lot to persuade.