There are absolutely laptops with fingerprint sensors.
I'd say the main reason it's more common in phones than computers is because of the different markets. Phones are mostly consumer purchases, the business market is smaller and the software is more locked down so you can rely on a software disable better sufficing for those cases. Laptops are increasingly dominated by business use cases. Businesses have IT groups that care about security who would prefer models without biometrics.
Secondarily, you login to your phone a lot more often than laptops so the convenience factor is less impactful for laptops. So people don't consider the fingerprint sensor a mandatory requirement as much as with phones.
What about the fact that fingerprints make great usernames but trash passwords?
Perhaps the poor security and extra hardware and software are enough to discourage makers, they can add a variant with a FPS and if that doesn't sell at all they won't make many others.
Right. Fingerprint is something you are. Can’t be changed. Same for any biometric.
Useful as one part of a multiple factor authentication scheme at best but never on its own. Not to mention there are cases in the US where you can be compelled, forcibly if needed, to unlock a phone. But compelling you to “say” what your password may be covered under fifth amendment protections.
This is why I only use biometrics for website passwords and the App Store on my Apple devices. To unlock requires a password, which cannot be forced (though at least one judge kept a man in jail for contempt of court for not unlocking a device, which should be illegal under the fifth imo).
Laptop has keyboard, you can type your password with the same speed as pressing your finger and waiting for it to unlock.
Most casual users won't even know that their laptop has a fingerprint sensor.
When a company needs a proper security, they buy every user a hardware token like Yubikey.
But most of all, it comes down to the tradition. Manufacturers won't add fingerprint scanner because users do not demand firgerprint scanner. Users do not demand fingerprint scanner because they are used to have no fingerprint scanner. Try removing a fingerprint scanner from a phone, you'll see your sales drop like a brick.
When fingerprint tech first hit the consumer market (I want to say early/mid 00s?) it was more common to see laptops with fingerprint sensors. I think they fell out of favor for security reasons, IIRC at one point Mythbusters had an episode where they fooled it.
All Mac laptops do. And my work Windows PC looks like it has one but the company was too cheap to pay for it, so all it has is a spot that looks like a fingerprint sensor.
The following is just my own assumptions, take with a grain of salt.
Phones are often taken out to perform a quick task, then stashed back in a pocket/bag many times a day. As such, being able to unlock a phone quickly is a rather useful feature.
On the other hand, laptops are usually taken out to be used for larger tasks, and as such, do not need to be unlocked as often.
Fingerprint scanners add less value to a laptop than they do a phone.