Well i can think of two reasons -
1.) May be because it's value is more deflationary, as it uses certain measures to discourage unstaking and hence selling.
2.) Since people already have POB and VYB is a recent launch. People also want to hold and grow a stake of VYB.
But there can also be others.
Could be valid these points you make, not judging btw, just curious and trying to understand it :)