Use case

Date pickers are great, but sometimes users need to pick a range of dates spanning days, weeks, months, or even years.

It avoids having to use two fields like so:

(Yes I know it's the same date! It's just to show the two fields.)

Why would you use two fields when you could use just one?

Proposal

There's packages for date range pickers (https://pub.dev/packages/date_range_picker, https://pub.dev/packages/flutter_date_pickers) but it's not official and it's a part of the material design specifications. Android has this functionality so should Flutter. This should be natively supported in Flutter and as far as I can tell, it isn't.

(Source: Pickers)