I bought various cylinders that open with the same key. Thus I can open my garage, my flat, and my other small spaces with the same key.
Advantage too: the previous tenant wouldn't be able to access my home if they've kept the key. The landlord too.
And if there's an unlikely urgence ? Well, just break the door (it's a cheap cardboard-y one)
But frankly, I would do it even if it was forbidden, as long as the door wouldn't be reinforced.
/If I ever came to one of my properties and my key didn't work, you better bet you'd be evicted.
On your greater point, there are a million ways to skin a Roman senator. There are alternatives that don't require a smartlock and if an otherwise great tenant (or applicant) really pressed the issue, perhaps I'd go with another one. In the absence of that, I'll go with what's easiest and sensibly secure (which, by the by, a smartlock is).