Latin influenced an already existing language: English. Therefore, all the most basic words already existed. Things like pronouns, articles, particles, basic (versions) of verbs such as to talk and to eat, and basic nouns such as the seasons, earth, food, etc, meaning they didn't "need" a romantic word. They needed words for things that were being introduced to them by these new people, like a gladiator, not words for things they already knew about, like the sun. Also, because the most common words are used the most, they would resist being changed by the influx of French the most. If you use the word 'gaderian' (Old English: gather) once a year, it's easier for you to shift from saying 'gaderian' to 'assembler' (Old French: assemble) than it would be for you to stop using a word you use every day, such as 'æftar' (Old English: after) and start using "apres" (Old French: after).
To sum it up, all the most common words existed already in English before romantic influence, and since their frequency of use makes them more resistant to change, almost all of the most common words are of Germanic origin.
The following is not exactly on topic, but pretty related and, mostly, very interesting.
The words we use most of the time are these 100 most common words. They create the entire structure for the language, and are then filled in with rare and specific words. No matter what crazy animal you see at the zoo, you're going to use a slew of these 100 most common words, with the addition of specific information to convey details. Whether a lion hunted, a monkey climbed, a wolf howled, or any other thing like that, this is true. "I saw a monkey climb a tree, it was so cool." 'I', 'saw' (see, inflections are attributed to the root), 'a', 'it', 'was' (be), and 'so' are all on this list. You could change it to be about a lion roaring, but 6 of 11, more than half, don't need to change. By placing specific words into the framework created by the common words, we get a full language. This sounds obvious once spelled out, but I think it's a good way of understanding why 100 words make up half of the words we use.
If you are interested in something highly related, and incredibly interesting, look into Zipf's law. It's a statistical "law" (it isn't a law like gravity, it only gives approximations and doesn't hold in all cases) that explains a frequently occurring phenomenon in statistics. Basically, in a set (the words in a given sample of a language, such as a book or even all of wikipedia, works very well), the 2nd most common thing (word, in this case) is used 1/2 as often as the most common word. The 3rd most common word is used 1/3 as often as the most common, the 4th is used 1/4 as often, continuing on until you get to single instances. Single instance words, interestingly enough, make up a a large percent of words used. Check out https://www.youtube.com/watch?v=fCn8zs912OE for more information.