Most founder packs these days seem to include loot boxes, which may or may not be part of the motivation depending on what else is offered. In most cases, I would guess people buy in for access, and most of the other stuff is gravy.
Coming soon to Steam : Steam Crates.
Buy a game on Steam and you will receive a Steam Crate. Crates come in Bronze, Silver and Gold rarity. The Steam Crate rarity drop chance increases based on the price of the game and your Steam Level. During Steam Sales completing the meta-game objectives will temporarily increase your drop chances.
Steam Crates may contain trading card packs, profile backgrounds, emotes, and in-game items for Valve games and developers who pay into the system, some of which are rare. Steam Crates also have a small chance to contain 1 (Bronze) - 3 (Gold) random additional games. You may also trade 5000 gems for a Steam Crate in the Market.
You’re welcome Valve. I will take 0.5% of all Steam Crate income generated as compensation for my idea, and in 6 months I will be retiring. =)
I know it was well received with Guilty Gear.