Also, if the reason why quads and axels' BV are raised is because they're harder jumps and ISU wants skaters to attempt these jumps, why raise loop?
I think this goes back to pre-IJS consensus about the relative difficulty of the jumps. There used to be a chart in the USFSA rulebook with diagrams of all the possible jumps as if they were school figures and difficulty factors for each one. I don't know that those factors were ever used in any official way in 6.0 judging, but they give a sense of what some experts thought the relative difficulties were before the IJS scale of values came along and made it obsolete, although there are some apparent discrepancies, and the differences between singles, doubles, and triples are not on the same scale as in IJS.
In that chart (I'm looking at the 2006-07 version, which may be the last year it was printed in the rulebook), single salchow and single toe loop were both worth a factor of 2, double sal was 4 and double toe 3, and triple sal and triple toe both 6. Loop and flip were both 3, 5, and 8 for single, double, and triple respectively; lutz was 4, 6, and 8, and axel 4, 7, and 10.
So the thinking at that time was that salchow and toe loop were pretty much equivalent in difficulty and loop and flip were pretty much equivalent, and lutz was clearly more difficult.
The original IJS scale of values arranged them with equal 0.5 increments between the base values of the triples, but I think most skaters, coaches, etc., would agree that triple salchow is much closer in difficulty to triple toe than it is to triple loop, or put differently, triple loop is much closer to triple flip than to triple sal. The latest revision to the scale of values reflects that consensus.
But now, although lutz is still the next-most-difficult triple and is further in value from flip and loop taken together, the lutz value has not been raised and the triple loop is actually a little closer in value to triple lutz than it was a few years ago. I don't know why the values of the easy and mid-level triples were changed and not the lutz. Maybe such a change was discussed and rejected, or maybe no one in a position to recommend changes felt strongly that that particular jump was being over- or undervalued compared to the others.
......But, I need a clear explanation why ISU didn't raise the base value of 3Lz. Also, if the reason why quads and axels' BV are raised is because they're harder jumps and ISU wants skaters to attempt these jumps, why raise loop? i say feds..........
Thing is, although I can't skate, 3Lz looks so beautiful and elegant, and I really do wish ladies do this jump often. But I feel like because of the changes in the bv, ladies try to avoid 3Lz 
Still it is scarey to think medallists can get away with up to say a loop and no lutz or in some cases no real flip either.
