You can't seriously put Apple and "not paying for it" in the same post...
Maybe there are instances where having a warranty in place will get a unique, indispensible, one-of-a-kind piece of kit up and running faster than without.
For general-purpose gear, though, I really don't see the need unless you simply can't afford to replace something, or pay for a major repair if it breaks.
Place a lot of bets, and you can be sure the house will win.
Without buying a new one. Last two Apple problems I had they swapped the hardware out, in the apple store, on the day. If you have AppleCare, they will send you a new device out, then you put the old one in the box and send it back. Typical example is TCO is about £42/month over 2 years which is nothing for same/next day replacements and the entire lifeline for my business. Add business internet connection with SLA, land line, that's about an hour of income a month on all business comms, fully redundant with known downtime metrics. Then you can plan around that if you need to.
Like I said, if it's totally fungible then perhaps it's not worth it. For example if you run your outfit on a DS1054Z you can probably afford to chuck it in the trash if it goes wrong after the warranty is up and buy another one from Telonic.
Another typical example. You can't walk into a retail outfit and buy a decent laptop these days. Nor can you usually get a decent one next day. However you can get NBD swap with Lenovo on support. Or buy two. I bought two.
No bets made. Make yourself a business risk register and rank them. Pick the top item once a month and fix it. This goes a long way when things go pear shaped. I've been running Ltd for 22 years now and have carefully analysed many business risks and eliminated them. This is all part of continuous improvement which should be part of your quality mission. The smallest of companies benefit from this.
I just think if your business can't survive a couple weeks/months of downtime of any particular kit then you have bigger problems to worry about. It's not a good idea if your survival depends on all your equipment manufacturers being able to service warranty within days. Also what do people even have in their lab that can't be replaced on short notice with any generic off the shelf one?
You're 100% right but a lot of people don't realise if that is the case or not until it's way past too late. Most small businesses don't do any sort of risk modelling and amble around in ignorant bliss with their fingers in their ears going la la la la la while scraping it every month on credit accounts.
Dave made a very good point about investing in your business and good tools and support that covers them for repair or replace allow you to continue to do what you do. I'm not saying that's the only way but it's the one that tends to come up with the lowest TCO and sudden expenditure requirements at any time and helps manage cash flow and mitigate risks.