The payoff is that your creatures all get double strike, which is a really huge swingy bonus to give
There are plenty of Deathtouch creatures in the set, which play very nicely with effects like these
For example, if you own an entire base set that youre looking to sell (or display), getting each card graded may be worth it even if an individual card is worth less than $20 as having the entire set graded would enhance its overall value
Not only is it incredibly fast, but the scanner can capture multiple cards at once
Mayhem is pretty similar to madness, only that it forces to player to follow timing restrictions
To summarize, a deck full of deathtouch creatures is going to have enhanced defensive capabilities than most other decks, and dealing poison damage means you've got a leg-up in the damage race