All of these are government systems and as such have a lot of "Security Theater" baked into the software for compliance reasons. Any Tyler product has to abide by at probably half a dozen compliance codes and complex laws, such as captchas where they don't need to be.

This is also a big reason why it's so hard for a lot of this software to be improved quickly. Almost every change requires a long and drawn out approval process with various government agencies.

Could be a performance thing. If a database is stressed and you are unwilling/unable to scale or optimize it, you can use a captcha to cut automated traffic.