Vdg in Mosfet Datasheet
...but never Vdg...

I just opened the datasheet of the 2N7002
which does list a maximum rating for \$V_{DGR}\$. As I would expect it has the same value as \$V_{DSS}\$, both 60 V.

That makes sense as \$V_{GSS}\$ has a much smaller maximum value, that is because the values of \$V_{GS}\$ is limited to what the gate oxide of the MOSFET can withstand. For the 2N7002: \$-20V &lt; V_{GS} &lt; + 20 V\$

The maximum \$V_{DS}\$ can be much larger, many MOSFETs are constructed such that \$V_{DS}\$ can be much larger than the maximum \$V_{GS}\$. This is done by constructing the drain in such a way that it can handle a higher voltage. See the article on power MOSFETs on Wikipedia. Without this "high voltage" drain construction the applications for MOSFETs would be limited.

So if \$V_{DS}\$ can be much larger than \$V_{GS}\$ then the maximum \$V_{DG}\$ must also increase, it cannot be the same as the maximum \$V_{GS}\$ as that would limit the maximum \$V_{DS}\$.