Other commenters have mentioned better diagnostics / better imaging / other monitoring tools. I've always wondered why not increase the frequency of PSA testing

Other commenters have mentioned better diagnostics / better imaging / other monitoring tools. I've always wondered why not increase the frequency of PSA testing to provide a time series and reduce noise, instead of examining single PSA results in isolation? I think the normal recommended frequency 2-3 years. A PSA test is noninvasive and very cheap compared to other screening methods, so why not repeat it every 3-6 months or even monthly when there's an elevated PSA level?