That's assuming they don't become travel centers themselves.

That's actually another advantage. If they build travel centers around their superchargers, anyone with free supercharging (which is a large fraction of the current installed base) would prefer theirs over ones they have to pay for. But then they get all the people milling around buying coffee, burgers, phone chargers, sunscreen, etc.

For that matter they could go into business with the truckstop companies. Supply the charging hardware and expertise to install/operate/maintain them at the truckstops in exchange for a share of the overall take.

Several of the Tesla superchargers I use are at independent gas stations just opposite the gas pumps.

Once store owners see the value and demand, they'll likely support infrastructure for EV clients.