Of course, "DIY" here doesn't mean you personally. If there is an area of expertise you lack, by all means, reach a domain expert for help and bring him or her on board. I wasted 2 months of my life trying to become a graphics artist; my hacking suffered for it, my business suffered for it, and my RSI prone arm suffered it (not to mention the taste buds of everyone exposed to my "art work")

By "doing everything ourselves", we also learn how it works and we are in control. Accounting is a good example. It could cost us hundreds and we would not know that much about our finance. Until the day we have more money and we found a accoutant that we can really trust, we'll do it ourselves.