Do you have someone who has so much technical knowledge they are simply indispensable?
What would you do without them?
What would you do, if a competitor enticed them away from you?
Could you gleam all of their knowledge from them, quickly and accurately?
How would you be able to compile all of their knowledge, and then to make it all available to any other, or even all, of your workers?
These are questions many businesses have to face. Especially if you have a highly skilled engineer or mechanic who you depend on. Sometimes your engineer is just not available.
How would you manage if they were incapacitated for 6 months?
Go to the job market and try to find someone, anyone who has at least some of the knowledge you need.
At what price?
How long would it take to find that someone special?
What would it cost you in agency fees?
What would the new person demand in fees or wages?
Could you afford the money or more importantly, could you afford the time?