If most devices got updates for even 2 years, that would be a notable advantage. But they don’t so it isn’t.
In fact, even if most devices allowed you to unlock the bootloader so you could install LineageOS yourself, that would be at least a notable advantage for techies. But they don’t so it isn’t.
Fact of the matter is if you buy a $930 Samsung Note 8 today, the flagship highest-end Android phone available period, it comes with Android 7.1, which is already obsolete. It just got 8.0 yesterday, 3 months after its release. It will likely never get 9.0 and the bootloader is locked on many models including every one sold in the USA, with a Qualcomm SoC.
It isn’t a notable advantage.
Now Google is aware of this and has taken steps to address it in 8.0. Maybe the next device generation, the one that comes with 8.x out of the box, will get updates for several years. Or maybe not. I hope so.