At this point of your wedding planning, you should be meeting with all of your prospective vendors and thinking you may go off the deep end!! But not really, it is just a stressful time and you will get through it and make all the right decisions. If you have a wedding planner, she/he will take care of a lot of this for you, but you still need to meet with them. The main purpose for this is to make sure your personalities don't clash. There are times during your wedding that you will be spending a lot of time with them and you don't want someone whose personality you do not care for. The photographer/videographer, and the wedding planner are the main 3 you will be spending that time with on your wedding day. Also, you want to be sure to check over all your contracts with all your vendors to be sure you agree with everything you have all discussed.
There is usually a lot of money involved in a wedding, from beginning to end, so making sure everyone follows through as promised is essential.
If you need to meet with several photographers, videographers, musicians, etc. before you choose the right one for you, don't worry about the vendors you did not choose. This is YOUR wedding day!
It is a nice courtesy to let the other vendors know that you have chosen someone else but not a necessity.
So, yes, most meetings are absolutely necessary. Make the most of your wedding day BEFORE IT STARTS!