If your project is that small that you can manage and implement on your own without teams having to work together and if you don't care about older browser. In

If your project is that small that you can manage and implement on your own without teams having to work together and if you don't care about older browser. In that case you maybe have a point. If you work on bigger projects you will run into many problems really soon. Like some Safari strangeness when it comes to CSS. Someone using some old browser which you as a developer would never use but your user base still uses it and it makes 12 % of the revenue.