Fences
Sometimes genuinely no. But the times it is yes, it is emphatically yes, and the failure mode is expensive.
A residential boundary survey in this market typically runs somewhere in the low four figures. Taking down and rebuilding a fence that went in on the wrong side of a line costs the full price of the fence again, plus removal, plus whatever the relationship with the neighbor is worth.
Put that way it is usually not a close call. The survey is the cheaper of the two outcomes whenever there is real doubt.
Even with a survey, putting the fence a few inches inside your own boundary rather than exactly on it avoids a whole category of problem. It keeps every part of the structure on your property, it leaves room to maintain the far side without stepping onto the neighbor's land, and it means a small construction error does not become an encroachment.
Not legally required, and it prevents most fence disputes anyway. A conversation before the posts go in costs nothing. A conversation after they are set is a negotiation.
If you are getting a survey, mentioning it beforehand is worth doing. Some neighbors will offer to split the cost, and even the ones who do not are far less likely to dispute a result they knew was coming.
Also call before you dig. Missouri One Call, 811, is free and required. Utility strikes on fence projects are common because people assume post holes are too shallow to matter. They are not.