How do you define "web" and "centralized" here? The internet (not necessarily the world wide web) was created to be decentralizedWeb as the world wide web of HTML pages served over the HTTP protocol. And centralised as served by the handful of biggest players in each market.
Even early on big centralised portals were attracting users. Internet started to attract common folks as soon as some services grew big enough to become "go to sites" at which point word of mouth was crushing smaller players. People didn't use Neighbour Joe's Web Crawler for searching, people used something like Alta Vista. The market for shopping on the internet increased directly as a function of big commerce sites gaining popularity. The small players never enjoyed more than a fraction of the number of users the big players had.
It seems to me that this suggests common people who do not have an interest in technology want to rely on a single (or at most few) brand(s) of service providers which basically leads to a winner-takes-all market and that just adds into centralised nature. If your mother wants to buy something on the internet isn't the only clue she has called "Amazon" ? (Or some applicable local market leader, depending on the country.)
Even if internet itself was completely decentralised and people were using RFC 1149 to reach the net I'm pretty sure they would still be connecting to Amazon, Ebay, Google, and other centralised hubs.