- You decide to change a certain variable or property from number to string. Good luck finding out what breaks and what doesn't. I'm sure your users will eventually tell during production when they submit tickets.

- Your poor coworkers waste days putting console.log and breakpoints throughout your code because they have no fucking clue what the key/values of your objects are. Or whether certain keys are optional and values can be null. Whether something can be string *or* a number.

- You relive the same experience as your coworkers after you return to an old project weeks, months or maybe even years later. Because no human being memorizes every line of code they've ever written forever.

You probably don't need typescript when you add a little bit of interactivity to your static website, no. A webapp with a large codebase that will have multiple contributors working in? I assure you, you'll do everyone a favour when using typescript. Even your future self :P