can do worse than V

In "You can do worse than become a lawyer" (a more common alternative is "You could do worse than"), what does the "can" mean? Some people say it is used to indicate possibility, but there are different types of possibility. What kind of possibility does the "can" indicate?

In affirmative sentences, "can" seems to indicate a tendency, not tied to a one-time occasion. "He can be at home now" is thus an incorrect version of "He could/may/might be at home now," whereas "It can get really cold in the winter there" seems fine. Is the "can" in "You can do worse than ask John for help" an unusual word choice for this reason?

Note also that "can do worse" can presumably also be used with third-person subjects. E.g. "He can do worse than marry Sarah."

Solution 1:

The common expression is could do worse than, not can do worse than.

This is demonstrated by Google's Ngram Viewer:

The chart clearly shows that the could construction is far more common.

The use of can is a simple replacement of could, and it should be interpreted to mean the same thing as could in this context (in other words, possibility).

Any analysis of can here should be treated in the same way as an analysis of could. Focusing on definitions and senses of can is a red herring, inasmuch as it's meant to be taken synonymously with could in this phrase.

As an analogy, these two expressions are meant to express the same thing:

I couldn't care less.
I could care less.

Although some people complain about what they think is the incorrect use of could (because it means the opposite of couldn't), in point of fact, people use both expressions in an identical fashion.

Short of analyzing and prescriptively debating the specific word used (couldn't or could), the two expressions are descriptively synonymous.

In the same way, the expression can do worse than means the same thing as the expression could do worse than. It's just that some people have come to use can instead of could.