Quite a few states require you to collect sales tax on sales to customers in those states. Most have thresholds and you only have to collect taxes if you exceed those thresholds, but unfortunately most of those thresholds are of the form sales of at least $D dollars or at least T transactions.
$D is usually reasonably high, like $100k or $200k, but T is often 200.
So 200 people in South Dakota each pay $0.01 for an article on your site generating a whopping $2 in revenue...but you have 200 transactions so you owe sales tax on that $2. Same thing will probably happen in a bunch of other states.
And so there you are, with tiny revenues from many states, but having to register with their tax authorities, having to file tax reports (quarterly in most cases, but I think some may be monthly), pay filing fees in some (which might be more than your revenue in those states!), and of course actually send the tax money.
Now throw in other countries. There is VAT in the EU, for instance. Most countries have VAT thresholds, but those often do not apply to out-of-country sellers, so you might have to deal with VAT for European that comes and buys one of your $0.01 articles.
There are some things that help with this. In the US there is the Streamlined Sales Tax Agreement, which is an agreement between about half the states where if an online seller agrees to collect sales tax for all sales in all the participating states (even the ones that they do not meet the thresholds for), the states will pay for the seller to use a service like Avalara or Tax Cloud, which will handle the rate calculations, the filing, and all that at no charge to the seller.
But that only covers about half the states. Those services will handle the rest for you, but not for free, so you can't escape tax pain.
With VAT in EU, there is a thing called VAT MOSS that you can sign up for. You sign up for VAT MOSS in one country (Ireland is a good choice for US businesses), and then you just have to file one quarterly report with them listing your sales in all EU countries and the tax owed, pay that tax to the VAT MOSS country, and that country then distributes their shares to the others.
The VAT situation is considerably nicer than the US sales tax situation, because VAT is per country. I just have to know that a customer is in, say, Germany, to know how much VAT to collect. In the US, the sales tax depends on address. 123 Fake Street in a town can have a different tax rate than 124 Fake Street, and the seller is expected to deal with that.
If instead of charging $0.01 per article you make the site free to users and plaster it with ads and make your money from those ads all those tax issues go away. The money you make from the ads is just ordinary business income, that gets taxes as part of your corporate income tax. The tax is the same regardless of whether someone who saw the ad lived at 123 Fake Street or 124 Fake Street.