>you get to solve / create / build in all these ways.
Most of the time your solution is broken. Some examples I hit recently from giant companies, the PayPal amount input keyboard handeling is broken (Del button was not working), Youtube search inpout with it's dropdown can get stuck open and you are forced to reload the page , when you re-invent the wheel you probably are skiping or gorgetting to implement everything so your custom popup might appear outside the screen, or it does not implement Tab ordering correctly or is not accessible, or is not navigable with arrow keys etc. Where in other GUI frameworks you use the built-in one and on top of that all those GUI framework will let you provide/override a custom Paint function if you want (on top of existing customization) so you are not limited either in any way.
Most of the time your solution is broken. Some examples I hit recently from giant companies, the PayPal amount input keyboard handeling is broken (Del button was not working), Youtube search inpout with it's dropdown can get stuck open and you are forced to reload the page , when you re-invent the wheel you probably are skiping or gorgetting to implement everything so your custom popup might appear outside the screen, or it does not implement Tab ordering correctly or is not accessible, or is not navigable with arrow keys etc. Where in other GUI frameworks you use the built-in one and on top of that all those GUI framework will let you provide/override a custom Paint function if you want (on top of existing customization) so you are not limited either in any way.