WHY IT HAPPENS ANYWAY
The lender is not being unreasonable. There is just no process.
Two people can agree a handover in an afternoon. What they cannot do between themselves is move the obligation, because it is owed to a company that is not in the room.
The lender underwrote a person
They assessed one borrower and priced the loan for them. Requiring consent before that borrower is swapped is ordinary credit practice, not obstruction.
Consent has no usable route
In practice there is rarely a workable way to ask. So the market routes around the lender entirely, which serves nobody including the lender.
The mismatch is invisible until it fails
Everything looks fine while payments arrive. The gap between who owes and who holds only surfaces when something goes wrong.
The document never moves
Ownership paperwork stays with the original name for years, which makes the vehicle nearly impossible to sell again cleanly.