Because it never before had loot that dropped at varying levels. Thats why. This means even if you get a drop it might not be an upgrade. So if you got a drop at every boss then all you are doing is slowly giving yourself better chance of increasing your light. Its not game breaking, nor a complicated concept. If you got a drop every week from every boss, it won't be beneficial anyway unless the drop is higher than the one you have. Its still nice to get a drop though rather than moldering shards which don't even give hard mode loot.

Funny because in crota's end and Vault of Glass if you didn't get weapons you got shards and/or energy which still helped you progress. This time around you get nothing at all roughly 50% of the time. I had 1 run were 1 guy got a prize from the door he was the only person to get anything out of it. That same run we had another person get nothing from the door, golgoroth, or the sisters(we didn't beat oryx.) In previous raids you were guaranteed at least rare materials as drops from every part that paid out a possible prize. If you didn't get shards you got an armor piece or weapon. This isn't an old mechanic that was launched with the game it a new loot system that sucks. If you put time into a raid you should get rewarded for your effort(and I don't think there's a raid team right now that wants to carry anyone through this raid especially on hard.

Because before the drops when they did happen were at "max" light. You just needed shards to fully unlock that light level. Now it's very possible that the drop you do get is meaningless, unlike before.

So....are you completely opposed to changes or something or what? With your mentality, you were probably like: oh the thorn and tlw are fine, why change them? The vex and suros (pre vanilla nerf) are fine, why change them? Change is good. Change keeps things fresh. I hate bungie's current retarded system of raid drops. Ppl want raid kiosks and ppl want guarenteed drops yet bungie still sticks to this stupid ass RNG based BS for raid rewards. Heres a suggestion: implement a system where you get tokens for completing parts of the raid. At the end of the raid, you can go to an NPC to exchange those tokens for gear/weps. Stronger/higher light pieces of gear will need more tokens. Atleast this way, ppl will be sure to get something guarenteed for doing a raid and the amount of time it would take to collect a full set for one character would be roughly the same.