Cryptocurrencies are "walled gardens" which cannot reuse, trigger, or execute transactions with other blockchains. If Alice wants to execute Bob’s smart contract, she can only send cryptocurrency from the blockchain on which Bob deployed the smart contract. This lack of cooperation stifles innovation and forces users to place unwarranted trust in validators or centralized exchanges. Merging blockchains together into Block Collider is like building roads between buildings. Hypothetically, one could build a building that has everything, but in practice some buildings are built to work in, some are built to live in — as long as citizens want to be in multiple buildings at different points in time, roads are valuable and necessary.