This is an interesting subject: to spit or not to spit.
In the wine business it is almost a must to spit when tasting. A typical retailer or restaurant manager might see 40-50 wines in a single day, let alone going to a major tasting where there might 100s of wines to go through. No one could possibly taste that many wines and function or not develop a serious addiction. The answer of course is to spit as you go. Most pros will have a bucket at the ready and will project their samplings - along with their thoughts and opinions.
The problem comes along with a person who is new to the industry or feels that spitting is gross or disgusting. They will taste and taste and swallow, but (usually) they eventually realize that this is not the best scenario for working. They will begin to spit here and there and get used to it after some time eventually making a normal part of the tasting process.
I once had a client that would turn away when she spit so that I could not see her. Like I want to really watch that! She felt embarrassed by the act, but I was so used to it I would just chuckle inwardly.
Most non-pros (consumers) are uncomfortable with the practice. This is very evident at walk-around tastings where many, many wines are offered. There is almost always a high percentage of the crowd that tends to taste more than they should. They taste and taste and just do not realize that they might have tasted too much until it is too late: not a good situation. Many of these people would not consider spitting, "it is a waste of perfectly good wine". What they may not realize for one reason or another is there might be greater pleasure in the tasting and exploration process than in the getting drunk process. This, though, is a concept that many people simply do not want to get.
Wine offers pleasure in many forms, but many times that pleasure can be diminished by going over the limit. Spitting can sometimes be the difference between too much and just enough pleasure.