For a few reasons.

First, because there is no difference in safety to me -- if I report my card lost/stolen within a reasonable timeframe, I carry no liability with either a magswipe or a chip card. Therefore, from a safety perspective, I have no incentive to choose a chip card over a regular card.

Second, the big credit card companies (Visa/MC/AMEX) have all permitted the big card issuers in the US to issue primarily Chip+Signature cards as they roll out their EMV implementations, instead of Chip+PIN. As this adds no additional security from a user perspective, there is no point in me complaining to my card issuers to replace my magswipe card with a chip card, as the chip card will not require a PIN.

This hasn't stopped me from requesting chip cards where possible anyway, as an EMV-equipped terminal should still take Chip+Sig cards even in places where Chip+PIN is prevalent. However, only the very largest US issuers currently have the technology to issue such cards, and it will still be years before these cards become mandatory, so my case is more the exception to the rule.