If you are designing an application today, why would you use bitmap assets? Logos, buttons, icons, and other UI are all going to be designed in a vector graphic

If you are designing an application today, why would you use bitmap assets? Logos, buttons, icons, and other UI are all going to be designed in a vector graphics program, so just export them as SVG and be done with it. SVG is even supported well enough in web browsers to use without issue. Take a look at the Stripe website for example, most of the images there are SVG.