Although you say this, some scrapped Pokemon seem to be revisited in future games, and some are scrapped for reasons that have nothing to do with rejecting the idea.
The Deer/Moose Pokemon here seems to have been revisited twice: Stantler in Gen 2 and Deerling/Sawsbuck in Gen 5. Also, it has design elements in common with the Musketeers (Terrakion, Cobalion, Virizion, Keldeo), so to say that being "scrapped" means it will never become official seems to ignore the design history of the games. Every design that hasn't been used so far is a candidate for refinement and inclusion in the future.
The crocodile, possibly a water type, probably got an overhaul in Gen 2, and became Totodile, Croconaw, and Feraligatr. Just think about it: the design itself may not have made it to the final, but that's the same as most of the early beta designs. Most designs get refined over time to become something we might be familiar with now.
When you think about it that way, Jaggu, the Shark here, probably became Sharpedo, and the cactus may have been refined into Cacnea or Maractus, or both.
For another example, they "scrapped" Mime Jr. and Leafeon in Gen 2, but both were officially used (after refinement and design clarification) in Gen 4.