General gist of why I didn't implement it on my last pass (and why it wasn't implemented the first time the trackers were introduced):
The collection mechanic is actually very low value compared to the stat profile of the item. Seeing "0 collections" after a game doesn't tell you anything about whether the item was worth the purchase or not, as it's the only lethality+crit option and could have been the best (and an extremely effective) purchase regardless of how many collections you made.
The above is important because the trackers are meant to give players an idea of whether their item purchase was effective, giving them feedback to better navigate the item system in the future. I fear that including this tracker may be not useful, and in some cases, even misleading towards this goal.
With all that said, however, "fun" trackers like "noobs collected" could be a future space that's worth investing in, but it's always a slippery slope of our most engaged players (Reddit) always wanting more and more data, which is actually a non-trivial turn-off for the most casual folks. Definitely a point we're likely to re-visit in the future, and threads like this are helpful as they remind us of the demand some players have for the features. Thanks for that!
Lastly, I apologize for stopping in so late, been trying not to stalk this Reddit on my holiday break.