I have seen works in journals cited as
–Smith ([1964] 1979, 103)
I am assuming the date in brackets is the first publicaton date and the second date is the year of subsequent publication. The last number is the page number
If this is so, then why bother to put the first date in at all.
Because citations are used to track who cited whom, so you want the citation to accurately indicate the specific item.
So if the citation
–Smith ([1964] 1979, 103)
indicates that the first time the Smith book was published was 1964 why bother putting it in at all? Since the 1979 indicates the year of publication I am indicating for the source on page 103
Or am I reading the cite wrong?
Because that’s the standard and your paper will get rejected if you don’t follow the standards 
The citation should serve as a unique identifier for the source material you used. As a trivial example, let’s say that your reader wanted to look at the material from page 103 of the Smith work that you cited. What happens if the pagination is different between the 1964 edition and the 1979 edition? This will tell your readers which one to look at.
It’s also important to let your readers know when the material was originally published. Things have changed a lot in the sciences (both hard and soft) over the years, and if your readers are unfamiliar with the cited author the original publication date can provide useful information.