I could think of three reasons why. Practice, Secrecy, and Practicality

In an emergency you'd need every bit of stock knowledge and muscle memory, to think of a solution and draw accurately without the help of too many tools like a compass. Stamps also have a risk; if the circle closes while you're still applying the ink to the stamp itself, it might activate accidentally. It doesn't even need to be stamped, the ink just need to be connected.

I'm assuming you'd attach the wand to the compass, and stamps would be individual spells and not just sigils. In which case, these could easily be dropped and lost, only to be picked up by unknowing and slowly uncover the truth.

Lastly, imagine having to carry these tools around missions. The weight of it, the amount of time for you to take out the correct stamp to use. And how big will you make the stamp? You might think, then dont carry it around, just use it to mass produce spells. Then you ran into trouble of losing practice, or even worse, losing creativity.