I often use an ETB to carry my current deck and some extra singles I'm thinking of playing or trading in that case, capacity isn't about bulk, but about accessibility and protection for specific cards
These cards are not just game pieces, but also collectible works of art
To balance a 2/2 gold card for four at mythic rarity during a period when the average power level of cards was spiking dramatically is a tremendous achievement, and the natural back-and-forth moments he provided at the top end of classic Jund endeared him even to those facing him across the table
Bruse Tarl, Roving Rancher
As an enchantment, it is very difficult to get rid of, and the fact that it forces opponents' creatures to enter tapped AND gives its controller life makes it a must-include in any white decks
These are all things you have to solve forand all before ever sitting down and playing with the deck you're trying out