They rarely do. Each succeeding president for the most part retains the work of past presidents as they use them as precedent. The continuing evolution of the imperial; presidency. Notice how many executive orders Obama is reversing? Not many at all...
Of Obama's roughly 40 EO's, more than half revoke, amend, or supersede another EO. It's not uncommon for Presidents to play dueling EO's. Here are a few highlights:
One of Obama's first acts was to issue an executive order allowing taxpayer dollars to fund abortions or the promotion of them overseas. The original order prohibiting it had been written by Reagan. Clinton issued an EO overturning it. Then Bush issued an order overturning Clinton's order. Now, Obama's order overturns Bush EO.
Obama also issued an EO that overturned Bush's EO prohibiting embryonic stem cell research.
An Obama EO overturned the Bush EO that established Gitmo.
Obama issued an EO overturning the Bush EO regarding presidential records.
Obama issued three separate EOs on labor union issues, overturning Bush EOs on the same issues.
These are just Obama's high profile EO's. I have no doubt he's been busy overturning many more or, altering them with strategic amendment that changes the initial intent (as he did with his recent amendment to Reagan's EO regarding immunity for Interpol on US soil.)
Typical trick is to stay under the radar by issuing an EO that amends another with eye-glazing language, i.e "shall strike the word 'not' in article 3.1, Section 12(d), fourth paragraph, second line, and, except as provided in 905C, 115D, or 901 of the National Wool Harvesters Act of 1947 (50 U.S.C. 303-5c, 401-5e, and 491-4k), shall insert the word "all" in section 124.3(6-c)preceding the third semi-colon.
Few have the time or inclination to plow through all that and piece it together--least of all, the press. So it's hard to know the extent of what he's really done to date.