Because they age out of it. A lot of us on this board are adults who enjoy these shows, but the target audience is usually a very specific, young age range. Kids usually go through a series of "I'm too old for ______" phases as they go from toddler to child to tween, and the years between Kyoryuger and this new show are pretty much that gap. In terms of children, Toei would not be expecting a ton of audience overlap between earlier dino shows and this one.

The target audience for this series basically wasn't born yet when Kyoryuger came out.

Yeah, but they'll think that Toei is reusing a old show.

Except they won't, because they'll never have seen Kyoryuger, because they weren't born when it was airing. And considering the usual prices quoted for DVDs around here in Japan, they probably won't have any way *to* watch it.

Seriously, apply a little bit of logic when someone tells you something.

Could Toei reuse dinosaur again in 2020 ?

why would they? now you're just being ridiculous

Dinosaurs is more popular than any theme used by Toei.

Jurassic park and Godzilla are huge again.

There is a big rumor circulating at the moment that Ryusouger might not actually start until MARCH which would be very unusual to say the least.

The addition to that rumour is generally a miniseries (or postscript episodes for LP) to fill the gap.