So that hackers cannot spam you if/when there’s a data breach. You can buy them without ID from the phone shop or have them sent directly to your address but the supplier could still have a supply-chain attack.
I use one for Signal, one for banking and another for friends and family but signal is quickly becoming the primary.
I recommend using https://hushed.com you can get discounts through ‘The Hacker News’ website: https://deals.thehackernews.com/sales/hushed-private-phone-1-line-plan-2500-mins-12500-sms/
Lifetime access was $600 but now it’s $54.99 (£40.11). You can also get a free disposable from hushed as well.
You could also use a Pay & Go SIM card from many networks not this enhances security, not privacy in some cases where KYC and AML biometrics are mandatory.
Some U.K. providers include:
The countries that currently have biometric registration laws are Afghanistan, Bahrain, Bangladesh, Benin, China, Nigeria, Oman, Pakistan, Peru, Saudi Arabia, Singapore, Tajikistan, Tanzania, Thailand, Uganda, United Arab Emirates, and Venezuela. Those who are in the planning stages of implementing biometrics are Jordan, Lebanon, and Liberia. In Mozambique, subscribers can provide their fingerprints if they don’t have adequate ID.
In China, anyone registering a new phone number now needs to submit a facial scan. This is also happening in Singapore. Singtel, which has a market share of 50 percent, introduced facial scanning to its ID-verification process. All of this can be done from an app on the user’s phone. Nigeria also requires both fingerprints and a facial image.