Because probate law is state jurisdiction, probate varies widely in its details. However, probate does have common features as exemplified by the Uniform Probate Code (UPC), which is a comprehensive statute first promulgated in 1969 by the National Conference of Commissioners on Uniform State Laws (NCCUSL) and amended in 1990 as a model code that states could adopt to provide uniformity to state probate laws. So far, at least 16 states have adopted the UPC in whole, while the rest have adopted it in parts. You can see which states have adopted which parts at the Uniform Probate Code Locator.
One objective of the UPC is to simplify the probate process, especially for small estates, which reduces both the time and costs associated with probate. According to this entry of West's Encyclopedia of American Law, attorneys have resisted the simplified process (probably because it reduces the need for attorneys) and bonding companies have also resisted because probate unsupervised by the court doesn't require the posting of a bond.