Of course you do. How else will people know that you’re a real cyclist? I mean, they might figure it out since you’re, you know, riding a bike, but do really want to take that chance?
OK seriously, spandex is not required. If you ride slow and avoid hills you will never notice the difference. However, for fat guys like myself who like to ride fast and have to climb steep hills and ride long distances the spandex stuff does help with the ocean of sweat and avoiding chaffing.
I should mention that my cycling jerseys do not match my shorts which in turn do not match my bike. Unless you’re getting paid to race bikes that sort of thing is just sad.
When I commute to work most people are not wearing special bike clothes. They don’t seem to be suffering any. Fortunately for us sweat factories several clothes makers are coming out with lines of bike clothes that look like regular clothes. The prices are currently prohibitive but as cycling becomes more popular I’m sure the prices will trickle down.