Are they necessary? No art objects are. No mechanical watches are necessary these days. But we like them for emotions - beauty, admiration, respect, affiliation, and for this IMHO some tourbillons work really well.
I proudly own:
PSM Vintage Tourbillon piece unique
Omega Central Tourbillon blue dial
UN Freak 1 (carousel, a relative of tourbillon).
3 different GP Tourbillons under 3 gold bridges.
If the right opportunity presents itself I would love to add a few more 😀. For example the recently seen here 39mm LF Galet Tourbillon, what a marvel. Or another GP. Or DB29 Maxichrono Tourbillon. I can go on and on 😀😀😀.