Russia BRM-3K Armoured Reconnaissance Vehicle With 57mm Autocannon Firing Tests

This will come off as a whine, but how big will they go with IFV guns?  Do you remember the last "medium" caliber experiment?  The last one I recall is with the Expeditionary Light Tank by AAI Corp.

Before that the only people that played with them were the Israelis with their 60mm Hypervelocity Gun mounted on Sherman's (supposedly it was capable of penetrating T-55's...not sure if I believe that).

The new "big gun mediums" are a fad for a reason I can't latch onto.  We haven't seen a radical increase in IFV armor, you get less stowed kills, they're still ineffective against MBTs, they don't flex well into the anti-air role and for fire support/suppression they aren't the first tool in the box that anyone would reach for.

So why?