I'm not sure I'm understanding correctly - have you ever purchased these particular items you want to buy in the past?
Like other members have said, new items aren't always stocked in all stores when the coupons come out. I too have seen coupons for a new product that I'd like to try, but couldn't find it in the store - it's a bummer, but since I've never bought the product before I just figure it's not a big loss for me because I don't depend on getting it and I may not have liked it anyway. It would be nice to try, but if not, oh well.
Some stores stop stocking certain items because of lack of supply or low demand. A product may be popular in one region but not in another, so the manufacturer still issues coupons for it for those who can buy it, but since the product isn't sold everywhere, not everyone will be able to use the coupons. Sometimes manufacturers discontinue or stop producing certain items - case in point: I have a few NED coupons (No Expiration Date) that were issued in the 80s and 90s and the products are no longer made. I will never be able to redeem those coupons, nor will anyone else, since the items are no longer available - I just hold on to them because I think they are neat.
So anyway, I guess what I'm saying is there are products that I want to buy too, but can't. Sometimes you just have to wait until the product is available in your area or if you happen to travel to a different region, you may be able to pick up the item during your travels. I've received a few coupons in potlucks and as extras in trades that are for products that look interesting, but I've never seen before in my area. If it's something I am hoping to try, I'll look for it in the store, but if it's not there then I just put the coupon aside and pass it on to someone else who can use it.
What I personally find works best for me is to focus on getting mostly coupons for the things that I already to buy on a regular basis and a few coupons for things that I have not purchased before, but would like to try if I can find them or if there is a good sale. That way, I don't end up with too many coupons I can't use and I don't spend too much time/effort chasing deals that aren't actually available to me.
Hope this makes sense.
I will only be online every few days, so I may be a bit slow to respond.