Aggregation is not the same as matching
Bid portals like BidNet solve part of the problem: they pull a lot of public opportunities into one place. But aggregation just changes where you do the searching — it does not do the searching for you. You still log in, configure searches, page through results, and judge relevance bid by bid. For a contractor running the business, that is still a recurring chore.
And portals tend to optimize for breadth, which means more results, not necessarily more relevant ones. The work of separating the bids you can win from the ones you cannot is still yours to do, every single time you log in.