A "checking account" in the US is a demand deposit account that the depositor can write checks against and virtually always comes with an ATM/debit card as well. It never costs money to deposit money to this account, but if you do not maintain a minimum balance (usually $500 or $1000), there may be a nominal monthly fee.
The vast majority of people in the US and probably 99.9% of the slashdot crowd get paid via direct deposit via the ACH (automated clearing house). The exceptions tend to be people who work in cash businesses (bartenders earning tips, handyman types, etc.) and people who do not or cannot have a checking account. Generally speaking, those who cannot have a checking account are either illegal immigrants or people who have either committed bank fraud or have absolutely dismal credit. Those who do not (but can) have checking accounts are either very young and haven't gotten around to it or are dodging tax liens, alimony, or other court judgments and are trying to hide their money from authorities.
In the absence of a deposit account, most employers used to issue paper checks which would then be cashed by shady operators for scandalously high fees (in part due to the prevalence of fraud, because remember - they are dealing with the subset of people who cannot get a bank account, a large percentage of which is due to fraud issues). These cards are actually probably lower fee than the previous status quo and allow things like online transactions that most of the employees who receive these would have been hard-pressed to do without a bank account.
For many people in low-wage, low-skill work, particularly if they are young or have gotten themselves into severe financial trouble, these cards are probably not a bad option. If its the only option, though, that can certainly be a problem, but that seems to be fairly limited (the article mentions a single McDonalds franchise owner who is actually forcing these cards) and for 90%+ of US workers, this is a complete non-issue.