The Amazon solution here, with the stuff they've launched today is;
a) use Kinesis Firehose to take a stream of log events from your app and dump those into S3 (gives you decent-reliability replicated backups)
b) ETL those using COPY into Amazon Redshift (a column store; very fast full-table scans)
c) point QuickShot at Redshift to draw graphs
so, yeah – but most of the data you want likely doesn't fit in Excel (or rather most of the work is reducing the data in size until it could).
With BI solutions you can perform "slices" as they call it, of multi-dimensional data (cubes), and then represent that as graphs that can also be used for drill-down on one or more dimensions of said data.
When you have say 17 dimensions, these solutions are easier to use than using excel to try to do the same.
I have only implemented very simple BI solutions a couple of times, so anyone with more experience can correct me if I'm wrong.
Source: Experience in Wall Street, Fortune 500 risk management, and dumping stuff from SalesForce to make it useable beyond what our implementation would report (or what leadership could get it to do).
http://www.microsofttrends.com/2014/02/09/how-much-data-can-...
If that's not enough you can do SSAS Tabular + DirectQuery (although to be fair, that's no longer "pure Excel", but an end user likely doesn't care):
Excel is point and click and allows for a wide rang of programming skill. There are also a lot of plugins and of course you can work in offline mode. It is also easy to integrate old Excel data etc... And you don't need a full time programmer who knows javascript etc or some other language to produce something.
People love saying that BI/Data Science is 80% cleaning data (which may or may not be true), but I've found R to be the best for cleaning up 100k+ rows at a time.
"Too big for Excel" is, quite literally, a problem of the last decade.
Edit: typo small != big