Why don't compilers merge redundant std::atomic writes?

I'm wondering why no compilers are prepared to merge consecutive writes of the same value to a single atomic variable, e.g.:

#include <atomic>
std::atomic<int> y(0);
void f() {
  auto order = std::memory_order_relaxed;
  y.store(1, order);
  y.store(1, order);
  y.store(1, order);
}

Every compiler I've tried will issue the above write three times. What legitimate, race-free observer could see a difference between the above code and an optimized version with a single write (i.e. doesn't the 'as-if' rule apply)?

If the variable had been volatile, then obviously no optimization is applicable. What's preventing it in my case?

Here's the code in compiler explorer.