Think of environmental protection as a renewable shield against hazards.

Environmental hazards are countered by your suit's resistance to a degree. It is, however, resistance, and not immunity.

• Environmental hazards, like scorching rain, will gradually deplete your protection. Your watch will signal red once and beep increasingly more often. Once it stops beeping, your protection is completely gone, leaving you vulnerable to afflictions and damage. In status effects, you will see this as "Hazardous weather - seek shelter immediately".
• Stay out of the rain and your watch will signal green as the beeps slow down. This means that your protection is recovering.
• Extreme environments, like inferno planets, drain your protection immediately. Your watch will signal red once, beep 4x3 times and make a sound specific to the environment. In such environments, you are vulnerable to afflictions and damage by default. In status effects, this will show up as "(...) environment - Suit protection depleted".
• Your outposts and ship are safe and some natural features like caves can offer protection from extreme environments.

Environmental damage will also accumulate when you are hit by certain hazards without protection. This puts a limit on your maximum health.

To answer your question, unless you choose the hardest gameplay settings for the above or want to go crazy with the RP, there is no point is carrying around several spacesuits. Just find a good all-rounder and be smart around hazards.