Maybe I phrased it wrong. You could force him to give you troops. Just next time he'll tell you that there is nobody who want's to join you. Same in villages. You can conscript them, but if you keep doing it, peasants start hiding in the forest every time you get spotted anywhere near the village, or even they'll go on a journey to find less oppressive neighbourhood.
That's why I'm for a system where forcing peasants to join your army, over the current hard limit, is possible. It just decrease your relations with them, increase chance of peasant revolt, lowers prosperity, ect OR cost more. So it's meaningful choice, rather than free meat shield. That's gameplay reason - choices are fun, softcaps are more fun than hardcaps, relations with your citizens still matter.
As a bonus, if you have high enough relations, the first recruit could be cheaper or even free. Cus they love ye.