There’s a problem with people recommending ‘smart guns’: they clearly haven’t looked at the existing market for mechanical trigger locks, the best of which are still comically insecure enough that a six year old with a paper clip and two minutes can disable them. The market doesn’t have sufficient incentives to make gun locks as secure as bike locks, and it shows. Producing a more complex system for in-firearm locking, featuring electronics and biometrics, will not be profitable if people aren’t willing to pay a few dollars for a trigger lock that actually has tumblers.
There’s a system in place for gun owners who want to secure their firearms: gun safes. Gun owners who do not want to secure their firearms will not pay extra for an add-on or a special more secure gun, and people will quite reasonably resist any legislation that requires new firearms to have such features (Apple can’t keep its own products working reliably, and fingerprint readers aren’t very good at eliminating either false negatives or false positives — how could you expect Mossberg to do a better job, or for someone to want to add a battery pack to an object whose job it is to sit unused for its entire lifetime except in the rare situation that a home intruder appears?). Even if new firearms all had such a system, new firearms are not the majority of firearms on the market: unless the sale of older firearms was banned or older firearms were gathered and destroyed (two very unpopular ideas), the only result would be a sudden drop in firearm sales and a lot more import sales from overseas of older weapons; and, this is if we only account for legal sales.
One must also consider the culture of firearm owners. Firearm owners in the united states skew a bit to the right these days (although any group not firmly in the center and any group with legitimate concerns about the reliability of government-provided policing are more likely to own guns: consider the black power movement as an example of a decidedly leftist cohort with a pro-firearm stance based on a completely legitimate expectation that police would not protect their community), and are going to be suspicious of any mechanism that could get in the way of using a firearm when they decide they need to, particularly if that mechanism is coming out of a government they don’t trust. There’s also, at least within the subset of gun owners who are essentially functional, a culture of gun safety: children are taught how to be safe around firearms long before they are allowed to put their hands on them, and mistakes like poor trigger discipline or poor muzzle control are treated not merely as dangerous but as social faux pas that invite mockery (anyone who puts their finger inside the trigger guard is considered a buffoon from the hated out-group who doesn’t even know how to shoot a gun, and as a person whose presence is dangerous due to stupidity and incompetence). Legislation that interferes or duplicates the function of that acculturation comes off as tone-deaf and disconnected to people with that acculturation, even as it may protect the family of gun owners outside of gun-owning culture (who are at greater risk of accidental discharge because they are unaware of the kind of safety procedures that are drummed into infants in gun-owning culture); this legislation comes from the out-group and is for the out-group and thus seems unnecessary.