According to the Merriam-Webster dictionary, the definition of sober is not getting drunk or abstaining from taking intoxicating drugs or drinking alcohol. Being sober can also mean abstaining from using addictive substances. Someone who is sober is intoxication-free, that is, not drunk. But does being sober or having a sober lifestyle require continued abstinence from alcohol? Yes, at least according to the standard medical definition of sobriety, a common view shared by popular recovery programs like Alcoholics Anonymous.
Sober is used when someone has been drinking alcohol. It doesn't necessarily mean that the person who has been drinking has an alcohol addiction, it just means that their mental state is clear now because the effect of the alcohol has worn off or the person hasn't drunk anything. Sobriety actually means, first, not being intoxicated. It doesn't mean abstinence, as AA understands it.
In fact, the DSM psychiatric manual (which practically everyone who uses it, even the experts who write about it) does not contain any abstinence criteria for recovery (what is actually called remission). Addiction and remission refer to the absence of problems using or not using a substance. The dominant concept of sobriety is commonly understood as completely abstaining from a particular behavior or substance. However, what it actually describes is abstinence.
The definition of sobriety in textbooks is simply not being intoxicated at any given time. Sobriety means not being under the influence of a substance. However, the word is often used in different ways in different contexts. Many 12-step programs suggest that sobriety means total abstinence from never using the substance again.
People who are curious and sober may not intend to give up alcohol completely, but they may want to give it up for a short period of time to see if limiting alcohol consumption or staying completely sober in the future would be beneficial to their lifestyle.