Why is "Did you acquire, sell, or exchange any virtual currency in 2019?" required? While the updated 2019 forms may have this question is there any law requiring it?

Yes. Virtual currency is treated as any other investment property.

From the IRS:

Virtual currency is treated as property and general tax principles applicable to property transactions apply to transactions using virtual currency.  For more information on the tax treatment of virtual currency, see Notice 2014-21.  For more information on the tax treatment of property transactions, see Publication 544, Sales and Other Dispositions of Assets.

Also see this LINK for more information.