It has to do with historical stress. Some words, like лес, рука, земля and others (you can find lists of fixed phrases like рукá óб руку in grammar books) still show the old pattern. There is a tendency towards entropy in any language, that is, to remove the unusual things that do not fit the general pattern, and the fact that we see it in modern Russian is no surprise. See the first paragraph here for more examples with рука
http://ru.wiktionary.org/wiki/%D1%80%D1%83%D0%BA%D0%B0 .
There are odd stress things with verbs as well. One famous one, and I would guess that none of the Russians here would use it, is the verb родиться, which used to have stress on the last syllable. Yes, even in родилась, родился. А complete anomaly among verbs.