What other reason would you have to tether if it weren't to use it for a significant amount of data usage? What's the point? Your "legitimate" scenario seems pretty unlikely. I do customer support for POS systems over the internet on a DSL connection and have NEVER been unable to provide that support in 9 years because of a failed connection. Could happen, but the building might burn down, too.
By the way, I never suggested a concern for Verizon's servers. I hope they are more secure than that! That isn't the reason for the prohibition on tethering. If you are in such a mission critical position then your company shouldn't mind popping for the charges to legitimately pay for tethering or anything else you need to do for your job.
It's easy to meter voice usage, and you are required to pay for the minutes you use at a premium if you go over the allowed usage. Data service is no different, except you are not charged for minutes...you are charged for data. The two services may use the same bandwidth, but they are used in very different ways. You can be online for hours and use very little data if you are merely reading a very long document. But if you are downloading huge files to your PC, you could easily surpass the very liberal 5 GB limit in a few days. If you are talking on your cellphone, being on hold takes the same amount of resources as yakking a mile a minute.
Do you feel that you should be able, on your own, to determine legitimate use of your Verizon service? Verizon has explicitly banned tethering unless you PAY to do so, as do virtually all other carriers to my knowledge. If you don't like the TOS (which you agreed to) then go to a service whose TOS are more to your liking. Or maybe get together with a bunch of other folks who want to tether for free and build your own network. Then you would find out, I'm sure, that it costs money to build, operate, and maintain a service such as Verizon's and have enough left over to go to the bottom line.
When you have your own network, then you can make the rules. Until then, you are stuck with the rules of the network whose services you use.
Sure, you can ignore them and as long as you stay under the 5 GB limit, they may not catch you. But if they do, they can unilaterally terminate your service and charge you for the rest of your subscription obligation. It's in the fine print.