The World Chess Championship between Lasker and Capablanca in 1921 was organised as the winner would be the first to 8 points, draws not counting, and if this goal was not reached, the player with more points after 24 games would be declared the winner. Lasker forfeited after 14 games.
The winner of the World Chess Championship between Karpov and Kasparov in 1984 would be the first to achieve 6 victories. The match was suspended after 48 games.
Those are only two examples of extremely long scheduled matches with many interesting games. However, nowadays the matches are much shorter. The 2013 World Chess Championship was scheduled to be only 12 games, and the last two were not necessary so there were only 10 games!
Is there any particular reason why the matches are now much shorter?