They don't have to rely on ratings to continue the show. I think in times of the internet and demographic change, that's a pretty important point.

These shows, Kamen Rider and Sentai and especially Power Rangers, are built around ratings being almost secondary. They're nice. But the true driving force is toy sales. If you have massive ratings but poor toy sales the show can still be seen as a failure. And having a gimmicky toy collection helps sell those toys that keeps a show going. Batteries, Keys, Headders, or Shurikens. If you give people a reason to collect them all they will. And the same could be said of almost any children's show since the mid-80's where cartoons began being half-hour long toy commercials like MASK, Transformers, and He-Man. The trend is changing though. Steven Universe is popular and though it has toys and merch attached to it, it's not a purely merch-driven show. KR, Sentai, and PR always will be. And that's a pro because without the toy sales being strong we'd lose our favorite series'.

The quota is not based on the show itself so even if people rage about how bad the acting or writing is as long as it makes money there is no need to worry about shutting down the franchise.
Bottom line:
http://www.reactiongifs.com/r/make-it-rain-dollars.gif

@Sentai
Which is the point of the post. Because the shows are built around gimmicks, they don't have to worry about ratings. Which is, as the title of the thread says, a pro of bein a toy sale-driven show. (However there was a time when it wasn't the case.)

i guess when kids and adults have toys in their hands before an episode starts, it motivates them to watch the episodes and after it's finished, they either recreate the scenes with their imagination or watch the episode again to recreate with their toys. Or they buy the toys after the episode is finished and recreate scenes with their imagination or watch it again to recreate them.

This.
Personally, I don't buy many toys (I'm a renter so space is an issue, also, being 45 they're just not too interesting to me - so, I'll buy a Gashapon here and there), but I like that the most recent series weapons and assorted junk look almost identical to the toy version they're selling - as though they're using the toy prototypes. This is a big change from the 80's where your store bought facsimile was "close-ish" to the one that Han Solo used, or whatever.

The synergy between the promotion and product is hilarious to me (in a cool way), particularly in more 'serious' shows like Gaim, where the gimmicks are wildly ridiculous, tonally contrary and toyetic.