That doesn't prove that use of SPV/web wallets is causing the decline in nodes. It only proves that more people are using blockchain.info than in the past, which you would expect if bitcoin is increasing in adoption. The number of blockchain.info wallet users is also not an accurate representation of the bitcoin economy.
put some numbers into some scenarios. charts, hypothesis. instead of instantly debunking it because it doesnt fit your mindset.
blockchain.info was just one example. theres coinbase user statistics too. and multibit download stats. all of which can be compared to core downloads and node counts.
then when you link up all the users that there are. and put them against stats that only 288,000 transactions a day are currently happening. then you will see that people are not spending coins multiple times a day. but maybe once a week.
this is usually the order(priority first) of normal peoples rational thinking when looking after their finances
1. ease of use
2. security of holdings
3. using a self sustaining store that cannot fail..
for instance. many people prefer a bank account that allows them free 24/7 access to their funds with a swipe of a card far before thinking of putting it in a secure bank account that needs a signed check, that only operates 9-5. and far far before worrying about the banking institution as a whole and wanting to put funds into something decentralised and eternally self sustaining(gold).
and so. most people with < 1btc OR who dont spend daily, and mostly holding for 6+ months. dont care much about being a node. they will just sweep there privkeys into a web wallet and move funds out when the time comes. they basically have no reason to run a node.
those who have >$1000 would want a decentralised solution but if they are not spending daily. they see no need to run a node. so they would choose multibit or electrum as a bit more security.
those who have >$1000 and do spend daily would be more tempted to run a full node.
so now that you know that bandwidth is not really an issue(previous posts). the key to increasing nodes is not just getting more people adopting bitcoin.. because an increase of hoarder of bitcoin has proven to not help the node could.
but instead making bitcoin more useful. so that if people are spending funds more than once a week they have more reason to be a node. not just for security. but also the utility of it. also ensuring you segwit fanboys inform the community the importance of being full archival nodes and stop saying that compatible mode (no witness) is fine. aswell as not messing with the TX fee because that is also a buzzkill for usability