The browser certainly makes this convenient... until you have more than a few thousand cells. At some point even just having the whole table loaded into the DOM is too layout and memory intensive (except on servo, sometimes).

When you try, then, to work around those limitations, continuing to use the DOM for it becomes impractical. This gets especially difficult with a spreadsheet, where row and column size is user defined, and thus a scroll offset is a sum of all of those sizes.

I've done this several times, so I eventually settled on a bucketed, run-length encoded cache of row and column sizes, but keeping this data structure current was a mess. The mess further escalated since eventually I worked on an application where the row and column sizes could change in a different chunk with a network update, and that would need to be reconciled somehow.