Because they don’t work in version 2.5
No, they don’t work in 2.7.1 ;(
If you give the mine a small engine and fuel, it will successfully target hostile ships. It will only last until the fuel runs out, but you can make that a very long time if you select a low engine power.
Could you provide an example? I would love to have them set by my stabilized jump points, instead of building patrol ships everywhere. I did not realise you could even build mines.