"Upgrading" an OS at an enterprise/business level is a serious expensive undertaking.
There are multiple applications, both purchased or developed in house, that MUST be certified to work with the upgrade. There are training implications for the user based that must be addressed. The company internal call center must be prepared with training and scripts to respond to the inevitable calls. The IT department must develop, schedule and staff for the rollout. And so forth.
"Patching" an OS at an enterprise/business level is also serious undertaking. The IT department must evaluate these patches similar to above as well. If it is a "critical" patch, IT "may" roll them out after testing and planning. Upgrades and patches always break something in the enterprise world.
Bear in mind, the above discussion applies to organizations with 100's to 10,000's of usually Windows devices. The largest rollout I managed was over 100,000 PCs in 110 countries.
But you say, I don't give a hoot about big companies issues with upgrades and patches. It's just little old me with a Mac on autopilot updates. True too an extent. You are your own IT department.
Upgrades and patches to Macs can have similar negative issues as with a Windows machine. New features to learn, existing features disappear (i.e. Cover Flow), missing drivers (i.e. Nvidia), etc.
The difference here is you are controlling everything with your Mac. In a company, you are not. Now the OP (original poster) of this thread works in a small company and there is a debate about upgrading all the Macs to Mojave. This issue becomes a risk/cost assessment for them. The boss is taking the least risk approach by standing pat. When the risk becomes to high to NOT upgrade, they can go for it.
Ok, yada, yada, yada. My recommendations for an individual Mac user is to NOT blindly do a major OS upgrade at first offering. Give it a revision or two to work out any initial bugs. When you want to take the plunge, plan for a rollback just in case. That requires a backup of the current state and an image copy via software like Carbon Copy Cloner (CCC). Then if you want/need to downgrade back to the original OS you can.
I just went through this process using CCC to restore High Sierra after upgrading to Mojave. Mojave broke my photography workflow with the dropping of Cover Flow as well as driver issues.
(By the way after working with Windows in the Corporate world for decades, I was overjoyed to return my Windows laptop at retirement. I now have a 27" I7 SSD iMac and what a sweet machine. I wish I still had my 1984 Mac as a souvenir as well.)