This all said, there some valid reasons to limit. For example, if the Department of Education wants to buy 1000 laptops and there were 5,000 responses to the opp there is a significant lift/cost for reviewing and responding to each of these. What is more cumbersome for the government is when one of the 'losers' protests the award. This halts the delivery of the computers to the customer as it goes through a 3rd party (still gov) review. In the end, the original awardee generally gets the ability to sell the computers but by this time they are now 18-24 months old... This is a complicated system governed by a few thousand pages of rules called the FAR (federal acquisition regulations).
also, transparency rules should be rigorous enough to illuminate all ultimate beneficiaries (through shell companies and subcontractors) so that larry, his brother darryl, and his other brother darryl can't artificially muddy competitiveness and undermine fairness.
rather than the byzantine prescriptive requirements we have now, the simple, straightforward solution to all of these is to disallow consolidation in procurement, making the contract sizes much smaller in most cases. it's much easier to hide significant graft in a billion dollar contract vs. a multi-thousand dollar one. the federal government tries to use size as its leverage over price, but we should be using competition instead. make contractors compete each time for smaller bites of the apple, rather than giving them the whole orchard in a single go, which often leads to complacency and corruption.