You're saying the right things, but not necessarily for the right reasons. The reality is that most draft classes are still top heavy, despite changes over the years that made 19yo's more skilled on average and low-potential players less common. Usually, most of the top picks will indeed invest in the draft as long as they're not inactive teams, and this leads to the play-off teams not bothering, as the top players will likely be off the board by their pick anyway.
However, I think a lot of managers are too risk-averse when it comes to the draft, as 10k a week, 140k a season in the modern BB economy is chump change. The key word in the last paragraph is likely; those top picks won't have the points to scout the entire draft unless they've been saving up, so there's always a chance of netting a nice consolation prize at least. And if you don't want that new draftee, there's another team who will gladly buy him off you.
Even those that have a top pick seem far too hesitant to invest properly; this season, I had the 8th pick and decided to go all-in on a whim by scouting the entire draft. Out of the 7 picks ahead of me, 4 were 100% active and none had gone bot. Yet I not only end up with the best player in the draft at #8, I also get the 4th ranked player on my board at #24. HoF 18yo, HoF 19yo.
Of course you're usually not going to get this lucky or have this many leftover points, but you've got to at least give yourself a chance, because what really is 10k or even 20k per week in Buzzerbeater?