Many users use password managers. That's why entering password more often or less often doesn't make much difference.
- It seems to encourage easy-to-remember / easy-to-type passwords over longer stronger passwords
It depends. For users that care about security there may be no difference - entering password every couple of days may be as hard as entering every couple of hours. If they want to use some simplifications, they would do that in any case. For users who do care about security there will also be no difference, they would not see much difference between entering password every couple of days or every couple of hours.
- There's more chance for a keylogger to intercept a password
If there is a keylogger running, it doesn't matter how often you enter the password. One time is sufficient.
- There's more chance for a physical observer to watch you enter a password
That is true. But if you are in a trusted environment, like at home, you don't care much if somebody observe you. If you are in a non-trusted environment, then you should care about observing even if you enter password once a year.
- It may desensitise users and lead to them automatically entering their password without checking a url
Again, it depends. Users that don't care about security will not care more if they enter password not so often. For users who do care there will be no difference if it is couple of hours or couple of days.
By invalidating user sessions you make sure that the same user communicates with your application. If user left the device (Laptop, PC) unattended and not locked, smb. else may use it. Yes, it makes the user experience worse. But it happens often that security conflicts with usability.
Mobile devices are left unattended and unlocked not as often as laptops and PCs. Besides, Google doesn't control laptop or PC Google. Where as on Android Google can control it fully. In particular, Google knows if you have automatic screen lock activated or not. Try to deactivate it, reboot, clear cookies, log in, and check if you will be logged out after some time.