Why not
sign your work? That's what made all the famous artists famous. Just amagine, back then, that was their way to validate and market their business. So I think it's the same for us. Customers should be proud to display our work!
In the first place, it's not your work, it belongs to the client that paid for it. Secondly, making
signs has nothing whatsoever to do with art or ancient systems of patronage. Patronage being the only way art survived 'back then'.
Signs are a commodity, not art. Making
signs requires mere skill not any sort of innate talent. While few might ever be able to paint a decent portrait or landscape or whatever, most anyone can learn the skills necessary do do journeyman
sign writing. That it takes a long time and most don't bother to become even passable at making
signs doesn't mean that this is not the case. Moreover, someone displaying a
sign doesn't give an ounce of clotted wombat snot who made it.
The people I see that brand their stuff are usually the very ones that should give serious consideration to taking up some other line of work. They don't seen to be very good at doing
signs.