Pinned straw:
@Parko5 I tend not to touch agri-businesses due to their cyclical nature, dependence on weather, complex supply chain, and susceptibility to what happens internationally (under-/over-production, commodity prices, wars, etc.). It is therefore a convenient sector for me to not have to invest time in to become sufficiently expert to invest. I also have little in my skillset or personal experience that puts me on a near level playing field with others.
So, it is as much about personal focus, and knowing my strengths, than a sweeping generalisation about the sector.
You say "And there are some industries I will not touch. Like airlines. "
Personally I have a whole list of sectors I won't touch (unless it's a REALLY compelling case) : Construction, telecoms, biotech, mining explorers, mining services (mostly - they're cyclical, competitive and capital-intensive), childcare, aged care, REITs, insurance, airlines, agriculture (they very rarely have decent ROE, and too many things can go wrong), fund managers, oil producers. Any suggestions for additions to the list? :)