Yes! It's not like people who don't want them have to use them (just like I don't use ball caps. Ugh! I wish I could take them off of the "work clothes" of some of my Sims!)
I actually do have some in my game as custom content. I use them for formal situations and sometimes for weddings (although I'd also like some nice wedding veils that are not CC!)
Frankly, these days tiaras are not just for royalty or formal situations. My friends and I all have tiaras. And we post selfies of ourselves (or in my case, my cats) for "Tiara Tuesday"! They are fun!