Back in 1999 the on-line market was small, and whilst there was a large benefit from ecommerce their were not a great deal of customers, however the first movers gained a lead and in most cases have held there advantage. The benefits of ecommerce have not changed, but it is now much more competitive and you need a better system to attract and keep customers
There are still a surprising large number of businesses and markets that have not yet embraced ecommerce. However there are much more businesses providing ecommerce than the previous catalogue and mail/phone order, because the barriers to entry are much lower and the business is much more profitable. The profitability of ecommerce businesses means that they can spend significantly more on marketing, and spends of 10% of turnover are quite normal for online businesses, and typically double the traditional spend.