Because with big enough project you have 2 ways: You update dependencies as a full time job and it bites you because something breaks big way. But most likely

Because with big enough project you have 2 ways: You update dependencies as a full time job and it bites you because something breaks big way. But most likely you have some help to fix it and as you are on top you might need to put work to fix it but yeah still full time job. You neglect updating dependencies and it bites you and you don’t even expect it just because you have to update something you did not expect will need it and you are now scrambling to do anything because you are messed up. Besides I like writing my own code more than dealing with some lib shenanigans.