You're not naming the "reasons"
One that I see and I'm curious about the others:
You take cheap player, and buy for 5x - this way you can transfer money from team to team.
this can be easily countered for example: if you buy from your 2nd team, your 2nd team doesn't get the money(reason - taxes and inflation
).
This way we have legal and fair way to transfer player from team to team, with cost to be paid.
You don't get any advantage of having second team, because you 1) pay the cost 2) others are available to join the trade