If you’re asking “why not multiline lambda syntax” then there are years if not decades of previous iterations of this exact question that you can find on the mailing list and then these forums more recently. You’ll note that despite this long history, there are still no multiline lambdas, so that’s probably unlikely to change this time either.
Here’s a blog post from Guido in 2006 explaining it from a design rather than technical standpoint: Language Design Is Not Just Solving Puzzles