It is a lot of trouble just to get that little bit of Mana, especially when mono blue Commander decks are often stacked with Mana rocks such as Mana Vault, Sol Ring or even a Thran Dynamo if all you need is colourless Mana
Goblin Trenches requires quite the investment of mana and lands but you only need to activate it a couple of times before youve overwhelmed your opponent, especially if you throw in some goblin synergies or cards like Hellrider
For two mana, the instant made it so target player couldn't cast instants, sorceries, or activated abilities requiring an activation cost
For example, Raffine, Scheming Seers controller draws X cards and discards X cards, putting a +1/+1 counter on a creature you control for each nonland card discarded this way
Based on my and others' understanding so far, you could potentially put all of your creatures onto the table from your deck if you build it to do so