Dimishing retunrs

Why do so many people deny this "theory". I've seen plenty of people saying that Bitcoin will give greater returns in the future but with every halving the gains get smaller

https://preview.redd.it/fi1an15emhfg1.png?width=814&format=png&auto=webp&s=3334f7e15cf59dc59229b41b0bcf23e2e831e007