This is really similar to the way lobbying works in government. Most lobbyists aren't blackmailing or directly buying government officials (that happens, but is often illegal and, when legal is wideley considered unethical, even among other officials, at least in the USFG). Instead, they're educating them. A typical, say, US senator doesn't have a staff that can be thoroughly expert on every topic on which that senator might need to take a position. Those topics aren't limited to things that might be affected by legislation; they also include things that might be asked of the senator in a news conference, etc. This is overwhelming, even for an extremely well-staffed office, and many offices are quite minimally staffed in non-election years.

Enter lobbyists. Their pitch isn't that they're unbiased, or that they're going to give the hypothetical official a huge kickback, future job, or secret bag of cash under the table (this sometimes happens, which sucks, but is not inherent to the practice). Rather, the pitch is that, while they are biased, they will inform the official about a topic they wouldn't otherwise know--or even know they needed to know about! Consider an about-to-break scandal in a weapons manufacturer that has been manufacturing malfunctioning guns, or some other relatively obscure topic (e.g. something massively overshadowed in the officially staffed military-research department by, say, headline items like the F-35 fighter expenditures). A lobbyist for that weapons company visits an official's office and gives them a rundown on how that company works, why its practices are (supposedly) ethical, how the malfunctioning gun works, et cetera. Now, whoever is listening to this pitch (and many/most lobbyists aren't heard directly by the senator/official who runs an office) knows this lobbyist's bias, but they also know that this is valuable information, because the choice is between knowing nothing of an area and being, albeit biasedly, prepared for upcoming press-ambush questions or similar. This can also help direct in-staff research.

Now, is this harmful? It definitely can be. But just like the PR-provided "journalism" discussed in this article, it may also be the only way that some information, however biased, gets into print in the first place. Given that most people don't (or don't have time/resources/ability to) do independent primary-source research on anything that might be newsworthy, I'm not prepared to universally condemn this practice.

Aside: there are a few limited alternatives for USFG officials to get information from. The Congressional Research Service can prepare briefs for offices who don't have the staffs to research on their own, and there are many other similar options, but you still have to know what to ask for information about. Vested interests (lobbyists) are very good at filtering for relevance . . . to their own interests, which is sometimes better than nothing.

There's also no reason constituents, or groups thereof, can't request an appointment with an official's office to convey info, just like lobbyists. Lobbyists are often given preferential treatment in such situations because they're known to be useful and informative (though there are certainly plenty of cases where they're given that treatment because they're offering kickbacks and take advantage of corruption and/or greed on the part of the people they're meeting with). Again, I'm not defending lobbying in all, or perhaps even most of, its forms. But I do think that lobbying, or PR-provided news, are not inherently unethical practices.

EDIT: so many typos.