They aren't really providing a service, but they're getting between confused people and public services
Consumer finance journalists complain a lot about their sites appearing before the real thing in search results
"You need this sign in your break room else you'll be fined $10,000! Just subscribe for $299/year and we'll mail you labor posters each year." These can be found for like $10 and don't change yearly.
"This form needs to be filed else you'll be fined! Pay us $499 and we'll take care of it!" Free to file online.
Even forming a business in my state is like 2 forms and $125 and can be done all online. But if you were to google how to, you'd find all these people to "Help out" and it'd end up costing you $1000-2000 for their "Help".
The worse practice IMO is exploiting a captive audience. It doesn't matter how stupid you are if you're an Apple developer or an Oracle customer; these companies will bleed you dry for simply touching their product. The only path of recourse is antitrust settlement, which is a lengthy and unnecessary process that is inherently stacked in the favor of whoever can hire more lawyers. Because of this, companies have no motivation to improve a paid product. Instead, the goal is to make you reliant on it somehow and then increase the price. We see this in Netflix, Amazon Prime, Windows/Office365/OneDrive, Apple developer program/Apple One/iCloud/App Store, and YouTube's TV/subscription services. The most successful businesses in our daily lives are the ones that have dug their claws into us and refuse to be anything other than a parasite.
I'd like to distinguish between those that bring services closer to customers and those that hinder customers getting to the services they intend to use
I always tell people to expect a minimum of $1k/yr to maintain a business and that’s to pay for a registered agent, a virtual office, and a domain and website (I also recommend a CPA). A registered agent exists only to forward legal correspondence directly to the owner. A virtual office handles all of the mail (which includes the junk mail you mention but can be silently processed out using their virtual mailbox service). And a website to provide an easy means of communication (again with spam filters in place)
I never see junk mail and I have started 5 successful businesses over the past 20 years. Spam phone calls is a completely separate unsolved problem, however