"People marry because they love each other."
There are many other reasons: ecstatic romanticism, wishes of parents and/or friends, loneliness, the desire for economic security, etc.
"Having children increases marital satisfaction."
The demands of raising children rob time for relationship building and maintenance; there's often financial strain; these and other pressures result in exhaustion and short temper.
"A good sex life is the best predictor of marital satisfaction."
There are many other extremely important factors: communication, problem solving, quality of leisure time together. These are all more significant n maintaining a good marriage than the sex life.
"Half of all marriages end in divorce."
Actually, according to the 1990 Census, 8.6 % of the adult population is divorced in any one year; slightly less than a fourth of all adults who have ever been married have also been divorced.