First of all, because if enough of us don't take the vaccine, we're all at risk from the virus continuing to spread and mutate.
Secondly, surviving Covid once doesn't mean you're immune from catching it (or a variant) again later on. That link you shared states a 1 in 50 000 chance of developing myocarditis from a COVID-19 vaccine. This recent study [0] finds a rate of reinfection among the surveyed population of 121 in 34 500 males and 148 in 31 697 adults aged 18-39. Either of those is more than 2 orders of magnitude higher than the risk of that heart complication. And catching Covid a second time can also leave you with further health complications.
Finally, I just want to point out that the article you linked literally has this citation from the study author: > He says the new studies clearly show that the benefits of vaccination against COVID-19 outweigh the risks of people aged 16 and older developing myocarditis. Previous research co-authored by Balicer found that in this age group, becoming infected with SARS-CoV-2 made a person 18 times more likely to develop myocarditis — a much more significant risk than is observed following vaccination.
So if you're evaluating risk for potential heart complications, I'd think you still want to get the vaccine at the end of the day (barring any other, as of yet un-mentioned, health complications). [0]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8373524/