Idea about substitutions in team matches

Don't you think it would be much better to have NO substitution during half-time in team matches? After all, in other sports, sustitutions exist mainly to replace injured players. Here we would have a system where 4 players play 4 players and with no risk of having too much power for strong/rich clubs. I believe 4 vs 4 is fair, much fairer than a system with substitutions.