*shifty eyes*

"I know not from whence thou came, but thou art no child of mine."
YEET
- "I CAST YOU OUT!!"

Having two or more sets of dice in different colors allows you to roll more things at once while still being able to differentiate between rolls. This can make the game move signicantly faster.
Having a few extra dice bags that each contain two or more sets of dice means that you're ready for new players who don't have dice of their own.
Now remember that that there are many games out there, and they don't all use the same dice. Better get several bags of dice for each game.
And that's why I've got a sack of 120 d12s here.
- As you walk down the Hall of 1440 Doors, you suddenly find that gravity has shifted. Roll 120 d12s to determine your location.

I play Imperial Guard in Warhammer 40K, you bet your ass 4 dice sets aren't enough

I have a giant box of dice and I loan them out to my players, especially new players. At the end of the campaign, I let players keep the set they used as a memento :)
If I only owned four sets, I'd have run out a long time ago.

As a dm the 7 section bag I got that I sorted 20 sets of dice into has been a godsend.
Now we don't need to wait to see who I instakill with dragon breath.
- I ordered 7 sets of dice in different colours. One colour for each type of dice, 10 each. So I can easily find 5 D10s in my grab-bag: Pick the yellow ones

I remember rolling 20+ d6 in Shadow run to shoot at someone. Also evocation wizards in dnd 5e like to have a word.
Lastly as a GM I like to have 6 dice sets for one shots especially with new folks or at conventions. So I can hand out a set for everyone.
Also maybe I'm trying to justify owning like 12 or so dice sets. But they all fit in my large dice bag with compartments for each dice type. Also none of them are fancy dice. They are just easy to read high contrast single color dice. All of them.
- I have a mixed collection of plastic, metal, and fancy metal dice plus a one pound metal Zocchihedron. I make no excuses. As long as you're willing and able to carry them around to a game you cannot have too many dice, especially they're cool ones.

I always have a D20 in my pocket at any given time. The look on their faces when we play Monopoly and instead of paying for the hotel I say „this is squatting“ and roll the D20.

I’ve only ever played 5e and a game based on the FATE system. I’m the odd one out with just a single set of die I’ve used since the beginning.
- I think I would hate playing a caster or paladin if I couldn’t roll all 8d6 or 5d8 or 6d10 or my damage at once.
  Especially once you hit level 5, casters really want that second set. It can slow down combat a fair amount too and some stuff (like Empowered Metamagic) relies on you being able to see your entire dice roll.