>>1199Tires undergo constant changes in composition, tread patterns, materials, thickness etc. In order to adapt to certain track surfaces, temperatures, as well as even driving styles (if that is allowed via FIA). Tires never keep one singular composition, they undergo vast change throughout a season. This means that different tire producers may have advantages during one race were another may have a disadvantage.
Alex Caffi was able to get his result since the Pirelli tires out-performed its competitors in warm-track conditions. Diversification of tires allows for more competitive racing. Some tires may have increased performance during any race given the adaptability they must have in order to remain competitive.
Furthermore, having more than one tire producer compete in f1 allows for competition between said producers. Battles between producers encourage more innovative design and production.