1. There's something far less draconian than this in place for senior roles in civil service, where restrictions are put in place upon leaving for a period of (say) 2 years, to prevent you using information gained in the process within a relevant sector, and requiring approval of appointments for that period of time. [1]

2. That pretty much exists as it stands [2], at least for sums above a certain level (usually 25k). Similar rules exist for spend above £500 on purchasing cards [3].

3. In some niche sectors, there aren't a lot of competent people. There are generally a lot of people who think they are competent. It could be problematic in these areas (some of which are pretty important), but clearly this doesn't apply for all. Competitive procurement is the ideal approach, but it has many, many flaws when you know the system and how to game it. The big outsourcing companies have that finessed down to the N'th degree. Over-promising and committing to things that can't reasonably be delivered make competitive procurement a problematic system, but short of the ability to "blacklist" suppliers who inexcusably fail to deliver in bad faith (which would be controversial too!) this one seems hard to fix.

[1] https://assets.publishing.service.gov.uk/government/uploads/...

[2] https://www.gov.uk/government/publications/guidance-for-publ...

[3] https://data.gov.uk/dataset/42c4d19b-aef7-45d1-bd92-1167d2f8... (as a random example for purchase card payments above 500)