ok, I'll say something no one else has....

There is no actual law requiring you to wear a 'cycling jersey'.

Though I like wearing cycling tights or knickers for practical reasons, i prefer to wear comfy tops that aren't really intended for cycling per se. Typically i wear very lightweight merino easy-fit base layers during Spring, Fall, and winter. I wear other layers on top of that depending on the weather, but rarely anything very form fitting on top. One favorite combo i wear is a lightweight Smartwool pullover long sleeve merino wool top with a neon-hi-vis relaxed fit windbreaker vest with full zipper and pockets. That keeps my core warm but allows for breezy ventilation. Lightweight windbreaker vests or loose light jackets are great!
Polyester jerseys always smell funky after one short ride! This never happens with my other tops or with my merino.
I have a nice saddle bag on my bike and thus I don't need the weird back lumpy pockets on jerseys anyway.