All users crypto currencies are stored in multiple wallet locations. Every Bitcoin cold storage wallet is encrypted and stored offline.
WHY COLD STORAGE WALLETS?
Crypto coins stored in online wallets, are never 100% impervious to attack. Any crypto coins stored online will be vulnerable to hackers and security compromises. However, hackers cannot steal crypto coins that are stored offline in 'cold storage' encrypted containers.
Because of that, withdrawals are not available instantly.