Programmers are in a race with the Universe to create bigger and better idiot-proof programs, while the Universe is trying to create bigger and better idiots. So far the Universe is winning.
Programming language designers are in a race with the Universe to create bigger and better idiot-proof programing languages, while the Universe is trying to create bigger and better programming idiots. So far the Universe is winning.
There's a good lesson here for why you make decisions when designing a language.
If you add restrictions or remove flexibility, feel free to do so, as long as you aren't doing it to prevent idiots from shooting themselves in the foot. If it makes tools better, standardizes something (e.g. python's whitespace 'restriction'), or helps experts avoid shooting themselves in the foot, go for it.