According to the link below, it does appear that you must take an RMD, or Required Minimum Distribution, from your IRA at age 70½, or face a 50% penalty of the RMD AMOUNT that has NOT been taken, which is going to be much less than 50% of your entire account balance.
Why specifically this happens would be opinion based on my interpretation of the reasoning behind those that enacted the law.
I can tell you penalties like this are used to encourage behavior - you can't just leave your money in a tax-free account forever. The IRA is meant to help you build your savings for retirement, and at age 70½ you should be ready for retirement.
This means you must begin withdrawing the money - but that doesn't mean you have to spend it.
In the link below, there are outlines on what you can do to satisfy the required minimum distribution.
As it specifies, you can take one lump sum, or spread it out over multiple payments, and there's a calculator to identify what your RMD will be.
As noted in the linked page, you DO NOT have to take an RMD on a Roth IRA. If this is important to you, you may want to consider Rolling Over your current IRA to a Roth.