Additional tunnel interfaces are automatically created when GRE modules are loaded in Red Hat Enterprise Linux

Issue

When modules such as ip6_gre or ip_gre are loaded, the kernel automatically creates new interfaces such as ip6tnl, ip6gre, gre0, gretap0, erspan0. What purpose do these interfaces serve, and is it necessary to have them auto-created?

# ip -d link ls
(...)
12: ip6tnl0@NONE: <NOARP> mtu 1452 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/tunnel6 :: brd :: permaddr 3ea5:daab:97ca:: promiscuity 0 minmtu 68 maxmtu 65439 
    ip6tnl ip6ip6 remote any local any hoplimit inherit encaplimit 0 tclass 0x00 flowlabel 0x00000 addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 tso_max_size 65536 tso_max_segs 65535 gro_max_size 65536 
17: ip6gre0@NONE: <NOARP,UP,LOWER_UP> mtu 1448 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/gre6 :: brd :: permaddr aad:ad4e:3c80:: promiscuity 0 minmtu 0 maxmtu 0 
    ip6gre remote any local any hoplimit inherit encaplimit 0 tclass 0x00 flowlabel 0x00000 addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 tso_max_size 65536 tso_max_segs 65535 gro_max_size 65536 
20: test0@NONE: <POINTOPOINT,NOARP> mtu 1448 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/gre6 2345::25 peer 2345::26 permaddr 96d6:99ed:8436:: promiscuity 0 minmtu 0 maxmtu 0 
    ip6gre remote 2345::26 local 2345::25 hoplimit 64 encaplimit 4 tclass 0x00 flowlabel 0x00000 addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 tso_max_size 65536 tso_max_segs 65535 gro_max_size 65536 
21: gre0@NONE: <NOARP> mtu 1476 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/gre 0.0.0.0 brd 0.0.0.0 promiscuity 0 minmtu 0 maxmtu 0 
    gre remote any local any ttl inherit nopmtudisc numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 tso_max_size 65536 tso_max_segs 65535 gro_max_size 65536 
22: gretap0@NONE: <BROADCAST,MULTICAST> mtu 1462 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 0 
    gretap remote any local any ttl inherit nopmtudisc addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 tso_max_size 65536 tso_max_segs 65535 gro_max_size 65536 
23: erspan0@NONE: <BROADCAST,MULTICAST> mtu 1450 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 0 
    erspan remote any local any ttl inherit nopmtudisc okey 0.0.0.0 erspan_index 0 erspan_ver 1 addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535 tso_max_size 65536 tso_max_segs 65535 gro_max_size 65536 
    link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
(...)