After-hours support matters most where the business keeps running after the office closes. A few examples from different industries show what "24/7" has to mean in practice.
A restaurant at 9pm on a Friday. For example, a 40-seat restaurant in Queens has its point-of-sale terminals drop off the network during dinner rush. Card payments stop. The useful response is someone who picks up the phone, checks whether the internet circuit, the switch or the POS server is the problem, and gets payments flowing, even if that means a temporary workaround like a cellular backup. An emailed ticket number the next morning does nothing for that night's sales.
A law firm the night before a filing deadline. Say a 12-attorney firm in Newark has a paralegal locked out of their account at 10pm, with a filing due at midnight. Multifactor authentication reset, reopening the locked account and access to the document system all need a person with admin rights who can verify identity properly. Five minutes of help is worth the whole month's fee that night.
A warehouse running a night shift. A 60-person distributor on Long Island runs picking and shipping from 10pm to 6am. If handheld scanners stop talking to the inventory system at 2am, trucks miss their slots. Support has to cover the wireless network, the scanners and the connection to the warehouse system, at 2am, with someone who already knows how the site is set up.
A dental practice on Saturday morning. A four-chair practice in Westchester opens Saturdays. If the imaging workstation will not boot at 7:45am, the first patient is in the chair at 8. Weekend coverage needs to be the same coverage, with the same documentation.
A nonprofit with staff traveling overseas. For example, a 20-person nonprofit with program staff in other time zones needs help desk coverage when it is daytime for them and the middle of the night in New York.