Are nowdays "terrorists" actually terrorists?

[Macoleco]

For a long time, the head has represented control, main part of something, etc., and that without it, the rest cannot function.

So, this idea made me wonder, if terrorists want to create actual chaos, why do they limit themselves to the murdering of simple civilians? Why not go for the "head", meaning people with political power such as presidents, ministers, etc? By cutting the head off, you will actually create chaos in a country.

Kill a homeless, nobody cares. Kill the president, the country trembles. 

Could it be then that terrorism is a business, and it lacks a real purpose?