You basically do get that, but it's hard to work around indirections. If I'm in company A and I give money to an industry lobbying group X (and so do companies

You basically do get that, but it's hard to work around indirections. If I'm in company A and I give money to an industry lobbying group X (and so do companies B, C, D, and E), and then industry lobbying group X gives money to super-PAC alpha, and then super-PAC alpha donates to politicians Bob and Fred, then... how does that become digestible to the public? Some amount of "Company A's" money went to Fred, but it's gone through several fungible buckets since then, and you can't necessarily draw a clean link. Informally, it may (or may not!) be that Fred was told by someone that his continuing to get these kinds of checks was dependent on him doing a specific favor for company A, but probably not everyone who receives some money that was originally sourced at company A did.