Perhaps could it be that you have never had properly ripe, healthy cantaloupe? In US supermarkets at least most fruits are unripe, or rotten, or unripe and rotten at the same time.

For anyone unaware the most helpful signal for picking properly ripe melons is smell. Unripe melons will usually have no smell at all, while overly ripe ones will have hints of a rotten fruit odor mixed in, even while still being completely firm in feel. The outside of an uncut melon should smell sweet and fragrant through and through, and just one sniff should be enough to tell which fruits should be passed over without a second thought.

For already chopped melon a lot of times it's a gamble, and odds are bad. In the US at least most fruit salad preparers are barely payed, and likely not even given the basic authority to be selective about what fruit they chop up in the first place. Basically no one cares how properly ripe or palatable the fruit is, and so sadly-often it simply tastes like oh so much disgusting garbage.

Unfortunately melons are some of the worst-affected victims in the race-to-the-bottom world of modern mass-production fruit, along with apples, pears, tomatoes and olives. Like with humans when no one cares to begin with crime is much much more common.