While actually riding I just go by feel. I'm only concerned about numbers while training, which is mostly indoors or on a nearby 5 mile circuit loop. But in fast group rides the proof is in the pedaling. If I can keep up, I'm doing okay. Having a display of data in front of me won't help then. But it's useful in solo training sessions.
I took my cheap bike computer off my steel road bike a couple of months ago just to make it easier to clean the whole bike. Never put it back on properly. Turns out I really didn't care about that stuff while riding outdoors.
However I do use it for the indoor trainer. The sensor won't reach from the rear wheel to the handlebar. So I set the receiver/display unit on the table next to my indoor trainer. I just use the speedometer for interval training sessions, to maintain a consistent effort for the peak efforts and easy spins.
But for my usual rides I just use phone apps and check 'em later, after the ride. Mostly Wahoo Fitness, transferred later to Strava.
Oh, and recently I added a Wahoo Tickr. Mostly out of curiosity. Some metabolic issues have messed with my BP and HR the past year, so I was curious to see whether my subjective "how I feel" corresponded with my heart rate. And it pretty much does. Turns out using my heart rate for training wasn't adding much benefit. I do it, but it's not really telling me anything I didn't already know.
On the carbon bike I keep it as clutter free as possible. No point having a light bike if I'm gonna overpack like I usually do with my other bikes. That bike is mostly for harder training sessions close to home so I don't need to carry much. And I can check my phone app data later.
On longer casual group rides I usually take my hybrid and may not even remember to record to Wahoo Fitness or Strava. If I had fun it was a successful ride.