Dredge in the terms you are referring to it is another form of MtG masturbation since for the most part there is virtually no interaction from the other player before sideboard. There is no reason for them to make the Dredge deck that you are talking about viable in Modern other than to satisfy an extremely small amount of players while frustrating and upsetting a large majority. They are trying to create and foster a new eternal format and they can't do that with unfair decks that have to be attacked at specific angles from every other deck. It's ludicrous to expect them to unban GGT and Dread Return when things like Wild Nacatl and Bloodbraid Elf are too powerful for the format.
Decks don't run removal, sweepers, DRS, or counters? Among other things, of course. That's also just interaction with the potential modern legal cards which actually isn't that big of a shell.
The reason to make it viable is to diversify the format. To give people more decks to brew, buy cards for, and play with. Why would this upset the large majority? Unless you're talking about the trend following idiots who hate dredge simply because other people hate dredge.
Have you ever played the deck or at least seen it played? A GRIM LAVAMANCER, for example, can wreck the gameplan.
Dread Return is banned to prevent the full-on dredge engine from being viable in Modern. The main reason (IMO) why that deck is bad for the format is the pressure that it puts on sideboards. If you don't have a sideboard that can fight dredge, you lose. There shouldn't be a deck in the format that's a bad matchup for every other deck preboard and a dog to every deck that boards against it. That's not where we want modern to be.
They prevented the full dredge engine when they drew the line at 8th edition. Ichorid, putrid imp, cabal therapy, LED, breakthrough, careful study, etc...
Dredge puts pressure on decks that don't run counters, removal, DRS, or sweepers, among other things, MB. They would have a bad matchup... many decks have bad matchups, it's not the end of the world. Sideboard gives some silver bullets for those rare decks.
