Why are there out-of-date tower frequencies on the VFR sectional chart, without a NOTAM? I flew today to Salinas, CA and had a little trouble reaching Salinas tower (KSNS). The current VFR sectional shows the tower frequency as 119.4. However, apparently the frequency changed to 119.525 on June 2014 (according to http://www.montereybay99s.org/newsletter/July2014issue.pdf)

The current VFR sectional was issued in August 2014, after the frequency change. I'm wondering why (a) the frequency is incorrectly printed on the current VFR sectional, and (b) if it's an error why there is no NOTAM about it.
It's not a printing error. FAA sectional charts are updated only once every six months. In order to to reduce the number of NOTAMs due to sectional changes (which can number in the hundreds between cycles), the FAA provides a section in the Airport Facility Directory (AFD), titled "Aeronautical Chart Bulletin" that identifies changes that have occurred since a chart's publication. Pilots should check this section on each AFD update for changes on their intended route of flight. Once the change is posted in the AFD, the respective NOTAM is taken down.

Here is an image of the applicable AFD page for Salinas, as of the date of this answer: