once again, with the laaarge distances in space, it's extremely time (and maybe resources depending on what they got) consuming, what exactly is so precious about our planet's species to arrange such expedition while with thier level of scientific and technological progress they can surely observe and gain a lot of data from the distance?I thought about this more. Aliens could visit earth for very mundane or logical reasons. First they may just wish to catalog and move on, a simple probe or stop by to gain info and leave.
The other reason is that I am sure their technology will still need material for energy and maintenance. This is almost guaranteed. After a long trip in space stopping of to extract hydrogen from our oceans, or nitrogen from our air, whatever it is, might be needed to continue on. I would be there is a lot of valuable resources on planets like ours that would help them.
regarding the using Earth as a 'gas' station - once again if that's a really long trip they're on, the resources thay could extract (which will take a lot of time too and us hoomans would probably feel not so cool about some space wankers draining our oceans to be on time for their space hookup) won't make much difference so idk, that's too much of a Battlestar Galactica concept to me