I think it just comes in waves. Since the beginning of the year, I've received more spam texts and calls being silenced by my phone than I did all of last year.
A2P = Application to phone, essentially any SMS/MMS sent to a phone by an app or automated process, and not by a human just texting.
10DLC = 10-digit longcodes; in the US (well, NANP), "regular" phone numbers are 10 digits long. This is as opposed to shortcodes, which are usually 5- or 6-digit numbers (though there are some that are shorter) that are sold to specific customers after an approval process where all US mobile carriers have to sign off on their use cases. If you spam, you get your shortcode revoked. They generally cost on the order of $1000+ per month, while you can usually get a longcode for $1/mon or less.
Over the past few years the US telcos have (due to regulatory action, not of their own choice) started requiring that anyone using 10DLCs for A2P use cases need to register: who they are, how responsible parties can be contacted, and what they plan to use the numbers for. Don't do this and your messages will likely be silently dropped.