There are several reasons why many movies are still not available in 4K resolution. One reason is that the process of converting older films to 4K resolution can be time-consuming and expensive. It requires specialized equipment and expertise to restore and enhance the image quality of older films to the highest possible standard. Additionally, not all movies have been shot or stored in a format that is compatible with 4K resolution, making it difficult or impossible to upgrade them to the higher resolution.
Another reason is that the demand for 4K content is not as strong as some may think. While 4K televisions and streaming services are becoming more popular, many consumers are still happy with the image quality of 1080p content and are not willing to pay a premium for 4K. As a result, studios may not see a sufficient return on investment to justify the cost of producing 4K versions of all their movies. Additionally, some studios may choose to focus on producing new content in 4K rather than upgrading older titles.