Why some people do a lot of pregnancy tests even after knowing they are pregnant?

This is not meant to offend anyone I just want to know why some people do that, because I've seen some posts where girls show a lot of pregnancy tests that are positive and say stuff like 'this is from ... day and this is from ... day' and ask about the colour of the lines, I want to know what's the difference between the lines? Because they look the same to me.

I personally just had one blood test that the only thing that said on the paper was positive and never had like the 'opportunity' or whatever to do a urine pregnancy test or to check my hcg levels so that's why I'm asking! Thanks