Assumption is the mother of all FU's

The danger in your remark is the word usually. Been there done that. And even if the data you are dealing with initially had a header row, there is no guarantee that the next time you get that data from external sources will have (the same) header line or that they either left it out, changed the order, spelling, casting or even inserted line(s) before the header to add "comments" or "instructions". Excel is likely one of the most misused/abused end-user tools in the (ICT) world. I *never* assumer anything in Excel, not even correct encoding or default (date) formatting.