Why pay for LingoPie, LingQ, Migaku or FluentU?

an Language Reactor free tier create a similar to these paid apps? I give a fairly comprehensive answer to this question by looking at what LingoPie, LingQ, Migaku and FluentU say they offer and at what price, then giving a short tour of Language Reactor's features. 00:00 Intro 01:26 Lingo Pie 02:43 LingQ 04:11 Migaku 05:35 FluentU 06:12 Language Reactor (Free) Music by Steemtunes