So that I can bet on this bonus straight away
You really need to be careful with going for casino welcome bonuses as most of the time they are a setup and can actually work against you. They often have requirements like you must wager X amount of times before the money can be withdrawn or they might even label your account as someone who is unlikely to be someone who is profitable to a betting company (e.g. someone who is only interested in taking perks and running with the money). Be sure to read all the terms around your welcome bonus and make sure you understand them before depositing, so there is no nasty surprises like a free bet vanishing after the first 24 hours when you didn't use it up.