I actually work hard at concentrating during davening. The amount of interruption by collectors is unbelievable. There are many who are from Eretz Yisroel, who are raised with the notion that everyone who lives in America is rich. They are generally desperate, and many will press on if they feel you can give them more. I sympathize with their desperation, but I have a limited amount of money that I can spare (I do not splurge on luxuries, and I give more tzedokoh than I can afford anyway.)
Far more irritating is the pressure from countless yeshiva bochurim who are also sent with quotas, often at the expense of their own davening on time, and their own learning. The raffles are pushed and pressed. It is another concern when boys under bar mitzvah are sent to collect by panhandling (not a closed pushka). I consider it wrong and irresponsible. I usually make a note of it, and give the tzedokoh to the same organization or yeshiva bypassing the child collector. Can these children be taught to do their collecting without disturbing those davening? From Borchu until chazoras hashatz, one should not be mafsik to give. Collecting then is a michshol, and it is assur. Poskim discuss this.
I find it disgraceful that our young people are being trained in taking tzedokoh, not the giving of it. This mitzvah is so precious, but we are exploiting it by teaching our children greed.