Every forward-facing car seat that is new enough to use (i.e. has not expired) will have lower anchor connectors AND a top tether strap. Every single seat.
Every rear-facing car seat that is new enough to use (i.e. has not expired) will have lower anchor connectors. If the seat has 2 parts – like an infant seat with a base – the lower anchor connectors are only required on one of the parts… and you’ll find the connectors on the base.
If you have a car bed (for a preemie or medically fragile infant), or a vest, then you typically won’t find lower anchor connectors or a top tether – and will use just the seat belt to secure the restraint in the car.
If you have a booster seat – a seat where the child uses the vehicle’s seat belt across them as their restraint – you may find lower anchor connectors, top tether straps, one of the above, or neither of the above. Boosters work well with or without being secured to the vehicle with the lower anchors or top tether.