Here's why:
* "Myself" is a reflexive pronoun. It should be used when the pronoun refers back to the subject of the sentence. For example: "I hurt myself."
* "I" is the correct pronoun to use when referring to yourself as part of a compound subject.
Correct usage:
* Linda and I went to the store.
* The manager gave Linda and me a discount.
Exceptions:
There are a few rare cases where "myself" might be used in a compound subject, but these are typically informal or idiomatic. For example:
* "Linda and myself decided to go." This sentence is grammatically correct but sounds a bit stiff and formal. A more natural way to say it would be "Linda and I decided to go."
* "He invited Linda and myself." This sentence is also grammatically correct, but it might be considered awkward. It's often better to use "me" in this type of sentence.
In general, it's safer to use "I" when referring to yourself as part of a compound subject.