Isn't there some law in linguistics that says words tend to evolve toward whatever is

[Odin2005]

2. Language change is a battle between laziness and comprehensibility.

Laziness causes sound changes that destroy grammatical word endings. the need for comprehensibility leads to the creation of new function words (Like English's helper verbs and prepositions) and then laziness turns the function words into new word endings.

An example is the Future Tense in most Romance languages, which originated out of a fusion of the infinitive and the present form of "have" in late Latin

So Latin amare habeo became Spanish amaré, "I will love you". Notice how the stress in the Spanish verb is on the word ending that developed from "habeo".