It's important to conceal your identity because the internet is forever. Your comments, opinions, beliefs, embarrassing moments... all recorded (essentially) for life. This happens through administration changes, different jobs, life changes, belief shifts, different friends and partners, etc. Without anonymity, anybody can comb through your entire history to make any point they want. To justify any accusation about you they want using 'evidence' from years past. To stalk or harass. To fire you for daring have an opinion about something. Depending on your government, to arrest you for what you've said in the past.

A huge issue with the modern web is that everything is seen as a profit motive. I don't care how many billions of dollars tracking everything we do and tying it to our person is worth. I don't want it.