Because, by focusing on only 50-75 guys, they are short-changing themselves (and us) whenever a player superior to one of "their guys" falls to them, but they still end up bypassing him in order to take the inferior player, who in almost every single case (despite Patchick's mumbo-jumbo) fails to live up to their draft status.
Although I'm sure we'll always disagree on this (and that's okay), "draft status" doesn't mean anything to me and I doubt it means anything to BB. For me, once a player is acquired by the Pats (by whatever means), the only thing that matters is how well he performs. What round he was originally drafted in becomes irrelevant.
That said, "draft status" certainly DOES seem to mean quite a bit to some other teams. I lived in the Detroit area for about 50 years and it was very clear that the Lions would frequently give their high draft picks the game snaps while leaving superior players on the bench who were drafted later. It was also pretty clearly an ego thing on the part of the ownership/front office.
For example, on the Lions - at least the Lions of my past, local experience - Malcolm Butler would never, ever have become a starter. The owner/GM would have insisted on sticking with their 1st-round CB even if he sucked.
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During the lead up to previous drafts - when the Pats have had 1st/2nd round picks and/or more picks, people like Pioli have said that their draft boards have included 125-150 prospects (still lower than most teams). So, the lower number this year may simply reflect a focus on a limited number of positions due to having fewer and only much later opportunities. I mean, it seems possible to me that the Pats are focused exclusively on DE/LB and OL with their first 3-4 picks this year. Given the prospects that will likely remain available to them by #72, that may realistically be only 50-75 prospects who have the potential and who seem to fit.
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I'll confess that I was disappointed when the Pats failed to draft McClellin, Sheard and Ealy when they had the opportunity. I thought they were all potentially great fits at the time. It seems possible now that the Pats may have agreed, but that the timing didn't coincide with their priorities of the moment, and/or they knew more than I did about the abilities of the players that were already on the roster and what schemes they wanted/needed to be able to deploy that season and the subsequent couple of seasons.
Nink is a prime example. Even three years after he became a starter, many people on fan boards like this were still desperately clamoring for him to be replaced by a "superior talent" from the 1st or 2nd round. And yet, here we are, four SB appearances and two trophies later, after a few of those "superior talents" have come and gone.
Also, just because the Pats didn't acquire a player as a rooking doesn't mean that they were ignoring him or stopped tracking him. The draft is merely ONE method of player acquisition, and it should be fairly clear by now that the Pats' personnel department maintains an up-to-date dossier on literally thousands of players and college prospects.
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Again, our judgements as fans/amateurs about which prospects are "superior/inferior" are based on a minuscule amount of information compared to what the Pats have about the prospects themselves and about the Pats own plans. Their scouting department didn't just start paying attention to/watching tape on all these guys in the past year or so. I'd guess that they've been following at least a few of them since high school.
None of this means that they're "perfect" by any stretch. They DO seems to take many risks with draft selections that, in retrospect, were obvious mistakes - there was no "reward" there after all. This seems especially the case with the "injury-prone" prospect who they've taken in the 2nd (Wheatley, Dowling). OTOH, they've also taken risks that have worked out.
The bottom line for me is that we simply don't know anywhere near as much as we think we know.
