I've used a lot of these systems in the UK, but I don't work in that industry (I'd love to be corrected by someone who does!) but my impression is that these ma

I've used a lot of these systems in the UK, but I don't work in that industry (I'd love to be corrected by someone who does!) but my impression is that these machines are primarily slow because of a combination of awful software and sloppy guard periods around their operations in an attempt to help with UX. Some of the examples I've used are catastrophically broken; the machines in low-to-mid-tier supermarkets (ASDA and Tesco) are in this category. Some of the machines are so bad that they are obviously malfunctioning – extensive delays between scanning and registering an event on the screen, or failing to react to button presses, that kind of thing. The software on these machines is embarrassingly bad. These ones also have a deliberately enforced delay when scanning multiple instances of the same item, which is utterly confusing, though presumably intended to prevent accidental double-scans. Combined with the enforced "pick-scan-weigh" workflow they're a total pain to use. On the other hand, some of the implementations of this technology are great. The machines in the relatively higher-end supermarket Waitrose are fast and efficient; the settings appear to be tuned much more leniently. In smaller stores, there now seem to be quite a few with no weighing system at all; these are particularly great to use. Waitrose also has a pre-registered portable scanner system which can use either a dedicated device or a mobile app, and this is also a good experience. The impression I get is that manufacturers can tune various parameters to suit the shrinkage requirements of a particular retailer. I'd wager that in lower-cost supermarkets or those subject to higher shrinkage, these settings are more aggressive. It's a shame, because when the technology is well-implemented I much prefer using it. When it's bad, it's unpleasant being repeatedly screamed at by poorly-implemented bug-ridden software.