Liz, this is among the worst written help pages on wikitree. The suffix field cannot be thought of as an "at birth field" as it applies to almost no standard suffixes used. It is just silly. No one was a Sr. at birth, or a knt. at birth, or a MD/PhD/DD at birth, or an esq. at birth, etc.
George, using Sr. Jr. III, IV etc. as a generational counting system is a standard device which has been used for over 800 years (certainly since Henry II). It is almost impossible to discuss the Gascoigne family with 15 consecutive Williams without them. I agree it is usually not necessary, and I generally don't add these suffixes as they can just be clutter. However, they can be very useful for distinguishing individuals, and wikitree is the only place anyone argues they are wrong.
Here is my answer. And how the suffix field help page needs to be re-written.