Why? That's a serious question.

The reason liability protections exist for information services is because information services can't exist without them. It's not possible for an information service provider to be strictly liable for what their users post while having anything like a reasonable quality of service or cost. Think 10 hour moderation queues to post on Instagram, which costs $15/month, and requires using your driver's license or other photo ID to sign up so they can forward libel suits to you.

Requiring strict liability on the part of information service providers will likely drastically reduce the amount of free speech. Because they're going to aggressively take down/reject anything that has the slightest possibility of them getting sued. They won't suddenly morph into the town square because an unmoderated Internet town square is a filthy, ugly place that repels users and advertisers and hurts the bottom line.

That makes no sense, since the entire, explicit purpose of Section 230 was to free platforms from preexisting disincentives si that they could be free to “restrict access to or availability of material that the provider or user considers to be obscene, lewd, lascivious, filthy, excessively violent, harassing, or otherwise objectionable, whether or not such material is constitutionally protected” without incurring liability that would otherwise attend such editorial control.

You are literally suggesting that the price of Section 230 protection ought to be not doing the things to which Section 230 protection applies in the first place.

Also, I think it's wrong, in any cases, to think of Section 230 as a special grant of liability protection, any more than the preexisting different liability of distributors from that of publishers is a special grant. It's a recognition that online media enables models that would not be practical with the media for which the traditional liability roles for content developed, and that venues for content which wasn't pre-screened in detail but over which largely reactive editorial control was exercised was all of technically and economically practical on the internet, inconsistent with the premises of the classic publisher vs. distributor liability analysis, and already, at the time the Act was considered, starting to be stifled by application of the traditional publisher vs. distributor rules. We don't force bookstores to be neutral platforms to be free of publisher liability, because we recognize that bookstores aren't naturally going to be pre-screening content at the detailed level print publishers will, and it doesn't make sense to stifle them by forcing them to. 230 is the same idea, just for a business activity that didn't exist when the common law of liability was evolving.