From my understanding Armistice Day has always been marked by two minutes silence at 11:00 GMT on the 11th day of the 11th month, which was the time and date that marked the end of WW1. Post WW2 it was also used to respect those who lost their lives in both wars... In more recent times it's been associated all wars including modern conflicts, and as far as I can recall (I'm 59) the 2 minutes silence has been a regular occurrence on 1th November. The service would often take place on which ever Sunday was closest to the 11th November. My guess is this was due to the fact that a century ago it was more traditional to go to church on Sundays and dare I say that tradition was more practice back then than today, especially given our 24/7/365 working lifestyles.
Should we still continue to mark these events... Yes. Whilst with every passing year there are fewer and fewer survivors for WW1 and WW2, there are still families that have been affected by war and we should continue to support them by remembering those who lost their lives in battle.
You could equally say should we still continue with other traditions such as bonfire night. Should we really continue to "celebrate" what could only be classed a s an act of terrorism that occurred over 400 years ago ??