I like to kees things simple, and I do not like to clean stuff, so adding secondary fermentation is something that bores me... Should I do it instead? What are the advantages and resons of doing it?
A secondary fermentation can have benefits depending on what you want to do:
If you want to reuse or re-pitch the yeast in the primary, racking the beer to a secondary fermentor is a better way to go because you will get a cleaner pitch for the next batch if you do not want to wash the yeast. Washing is not hard just a little time consuming.
Another thing to consider, if you have a beer that will have additions of fruit, wood, flavorings, etc.. a secondary would be a better route again, if you plan to reuse the yeast flavor of the next beer will be minimally affected.
There are argument that putting a beer in a secondary will help with clarity. In my experiments I have not seen much difference. I have fermentation temp control and drop the beer to 33 degrees when I get to terminal gravity and have been happy with the results.
Lastly, if you are going to age a beer for an extended period it would be good practice to move the beer off the yeast. At some point the yeast will start to break down and have flavor impact on the beer.
There are a lot of factors that would go into how long this would be, as a rule of thumb I take a beer off the yeast if I am going to age 6 months or over. To go opposite of this I just took a Bretted wit beer that was in the basement for 1yr and 2 months, left on primary, the final product was outstanding. The beer was 4% ABV, the alcohol level in the final product was so low that the degradation of the yeast took place at a slower pace.
Hope this helps. Cheers!
The only practical reason I know of for racking to secondary is the improved clarity of beer. By racking off the yeast cake in primary gives the yeast a chance to settle out again which greatly improves the clarity of a beer. This was covered nicely in an experiment by Basic Brewing with a great pictorial example here: