Veracrypt is a fork of TrueCrypt, which was used by lots of low tech people (I know some personally). For certain use cases, it's pretty straightforward to use. I suspect that at that time, it was the simplest highly secure SW that was available to people: Free and open source.

Comparing with Bitlocker is silly - its source is closed, and that's almost an automatic "untrustworthy" for many. It also is Windows only.