SQL Server JOIN conditions

Every time I write a SQL statement that has a JOIN like this...

   1: SELECT      *

   2: FROM        Products

   3: INNER JOIN  Categories ON Categories.category_id = Products.category_id

I wonder why I can't just write it like this...

   1: SELECT      *

   2: FROM        Products

   3: INNER JOIN  Categories ON category_id

That's not so needy, is it?

Yes, I know tools like Red-Gate SQL Query Intellisense Tool ease this pain, but I've had problems with such tools and I've uninstalled them.  Plus, the code is still there, cluttering up my screen.  And code is bad anyway.