When you gain a level, you gain a point you can spend on a skill, either a new one or ranking up an existing one. However most of the skills and skill ranks have level requirements that immediately outpace your skill point gains (e.g. the ranks may require levels 3, 8, 14, 20).
Since there are more levels than possible skill purchases, it seems like it is optimal to wait until I reach e.g. level 20 and buy all four ranks at once, rather than spending the points immediately on skills I don't really care about.
Is this the case? Or did the designers actually maybe play Diablo II and realize how stupid it is?