Blog subscriptions widget is on front page,
every time page is generated an request is made to uri https://jetpack.wordpress.com/xmlrpc.php?for=jetpack
1) its remote
2) its https
and therefore is slow (adds at least 1 second), and because its made EVERY page generation (unless cached by object cache) it affects performance, thus doing too much remote requests isnt very nice for api server too.
maybe add in future versions of jetpack an option to just display form for subcriptions and dont make any query for subscription status?