My experience, from knowing quite a few business owners, is that they are always "angling for the edge." They want to squeeze every bit of advantage, out of every relationship/deal they have. Almost every relationship is adversarial and competitive. Lawyers can be the same way. The best ones, consider every interaction to be combat.
I'm not wired that way, so I'm not a particularly effective business owner.
In both scenarios, it really depends on how many alternative options for income you have available.
As employee, it's all or nothing.
All the ones I have dealt with have survived precisely because of their ability to get along with people.
If you have no people skills your small business will fail.
An employee doesn’t show up for work a few days in a row, you have to fire them the next day. Every day they’re pushing against the grain.
A vendor isn’t behaving? A business owner isn’t scared of using conflict to resolve the situation.
In my experience contractors are the most likely to be friendly, and small retail the most likely to be unfriendly.
In fact a lot of them do fail, maybe not coincidence. Also, "people skills" in some cases means being a manipulative sociopath.
The employee is spending someone else's money - they are more likely to be rational or even blasé about losses when it is not their money.
Relationship management is everything in running a small business. You have to get along with clients, employees, suppliers, customers, and do a good job so all of them continue wanting to work with you.
Just like someone in customer service might act differently with coworkers vs customers.