There is a price point/equipment grade where it makes sence getting a good level of kit.
For example - Tiagra is an excellent groupset - you can pay bits more here and there for better parts.
Can't say 've ever regretted buying Dura Ace for the best bike - it's been on the bike 22 years. I originally had a loose cup BB, but only changed that when the cartridge ones came out - bought the Dura Ace/XTR bb for about £70 (over 15 years ago) and haven't ever touched it - other than to remove to check frame and re-assemble. Same with the pedals - haven't once needed to service them, but they were top of the range. Headset was changed to a cartridge DA a few years ago because the old one had finally pitted. That was over £60 for the headset. When I bought the bike I had the spare cash, wasn't married or had kids. Would be very different now if I wanted to splash that cash again.
My commuter was a mix of 'good' long lasting parts - wasn't cheap, and was bought on a 'most durable and reasonable weight basis'. BB is a basic cartridge shimano - easy to replace if it fails - hasn't in over 3 years. Headset - fairly standard, but protected as have guards. Hubs - reasonable Formula ones - LBS recommended as it's easy and cheap to replace the cartridge bearings - also easy to re-grease ! Rims high quality Mavics - been re-placed 2-3 times now due to wear. Bars/stem - went near higher end as the weight/strength was much better than the cheaper ones. Got XT SPD's for about £45 - well sealed, and a doddle to re-grease.
You probably got your steel bike second hand - they are very good bikes - don't know the kit on it, but if looked after and maintained they last.
Some folk like changing and modding bikes - better than doing it to a car ! Your money, do what you like with it.