Do most postdoc offers include travel funding?
None of my postdoctoral positions had travel funding in them, nor have I heard of anyone getting such funding.  There are several factors to mitigate this, not all of which may be available in all situations.


The postdoc can learn how to apply for grants and other things, which can provide the necessary funds for travel or other research needs.
If he is invited to give talks, then the inviting institution/department/professor will often cover travel expenses and offer a per diem.
He is likely coming there to research with specific people.  These people, being experienced, established professors who can attract promising postdocs, likely have grant money of their own, some of which could be allocated to the postdoc's travel costs.  This is often what pays for the previous point: professors can often use grant funds to cover the costs to bring in speakers.
Exceptional postdoc candidates are likely to be offered exceptional postdoc positions, with fancy names like The Harry Smith Postdoctoral Fellowship in Dynamical Systems.  These often come with bigger paychecks, making it easier for the postdoc to afford such outside costs.