Because the web distribution model for apps is extremely cost efficient. This has caused exponential growth in web app development. To support this, frontend fr

Because the web distribution model for apps is extremely cost efficient. This has caused exponential growth in web app development. To support this, frontend frameworks have grown almost exponentially as well. Every corporate app is a webapp nowadays. This wasn't the case 10 years ago. When we talk about web development, we are now not just talking about websites but about apps as well. So the industry has changed significantly. UIs always have been complex btw. A lot of different states, and keeping backend and frontend in sync is hard too. So many edge cases need to be considered, orders of magnitude more than in the backend. The UI is also your first line of defense against unexpected user input. Summarized: (1) app distribution has shifted to the web, (2) UIs are complex