TypeScript is awesome compared to JavaScript and even to other popular C-like languages. But it inherits all of the problems of the JS ecosystem without providing all of the benefits.
To make a JS package consumable by a reasonably strict TS project, someone has to basically rewrite the package. It's less effort than writing one from scratch, but it's not free.
> To make a JS package consumable by a reasonably strict TS project...
I’m not sure what you mean by “strict” here... Certainly one can use JavaScript from TypeScript, and even provide type information for the JS with declaration files. [1] Does a “strict” project require something beyond this?