The same issues happen in any other procurement activity that is required to rigorously follow a specific process due to spending public money, or bill-payer money of a regulated monopoly etc.

In short, you need large numbers of people involved to avoid "corruption" (irrespective of the actual level of such risk), and this means you end up less flexible and less able to buy what's needed. Weighting price by 80% is common, as nobody wants to be seen to deliver "poor value for money to the tax-payer". Hence the cheapest bid almost always wins, as nobody wants to have to stand up and explain why they didn't pick the cheapest bid.

There's a whole separate issue in how to handle "too cheap" bids (i.e. where you under-bid on the initial work, knowing you can get technical lock-in and be able to win future contracts uncontested, and turn those lucrative), but this is still an issue - see how the large outsourcers or consultancies do this regularly, and end up winning renewals on basis of "necessity".

There's an art to writing a winning (cheap) tender, then staffing it with people who rigorously enforce the scope back onto the Government client, and force every single change through an expensive change process. That's the business model many follow, and it delivers far poorer value for money in the long run. But the headline price was cheaper, so they'll still get selected...