Getting paid time off at your job can take some time. Unless you're an usually lucky duck or a master negotiator, you won't start a new job with weeks of PTO for you to take whenever you want. You will typically acquire it over months or years, saving it for a big vacation or a rainy day. While some people might have more PTO than others (for instance, if they negotiate for it), it's standard for every company hiring full-time employees to give them at least some time off. You've got to build morale somehow, and giving employees no chance to take a day off without missing out on income is not a great way to do so.
One employee recently went viral on Reddit for bemoaning his workplace's PTO policy. At his job, only employees who've worked for over ten years at the company are eligible for two weeks of paid time off, and that policy is ringing a lot of alarm bells.